Mario, Luigi, Princess Peach, Toadsworth, and the Toads are invited to Pi’illo Island by Dr. Snoozemore through a message that was delivered by his Broggy. They travel to Pi’illo Island on a blimp. During the flight there, Luigi falls asleep and dreams of Mario fighting Antasma. Afterwards, he dreams of the blimp that they were in to fall and crash into the Pi’illo Blimport, but instead Luigi wakes up and falls to the ground out of confusion. Later on, they reach Pi’illo Castle and re-unite with Starlow, where Peach and Toadsworth accidentally set off a test platform sending them to ancient Pi’illo ruins. Mario & Luigi follow upon pursuing the two through the ruins, find Peach and Toadsworth surrounded by a group of Smoldergeist which flee when the Bros. arrive. Here they find a Pi’illo, which later turns out to be Prince Dreambert. This action causes the Smoldergeist to come back and attack the Bros.. Upon beating the group and leaving the ruins the Bros. come to a collection room. Here Luigi takes a nap on the pillow. After everyone gathers in the collection room, a Dream Portal opens a portal to a place called the Dream World. This allows Antasma, unknown by anyone, to pull Princess Peach into the world against her will. After Mario chases after Peach into Dreamy Pi’illo Castle, with the help of a dreamy version of Broque Monsieur, he comes across Dreamy Luigi, Luigi’s dream representation, who assists Mario through his treks in the Dream World. Giving chase, the Bros. catch up to Antasma who creates Dreamy Mario to stop Mario, but upon Dreamy Mario’s defeat, Antasma creates a portal to Dream’s Deep and flees there, sealing it up afterwards to prevent the Bros. from giving chase. Mario and Luigi then find a Nightmare Chunk & break it, freeing Prince Dreambert. He then explains that there were two powers in the on Pi’illo island, the Dream Stone and the Dark Stone, both stones have the power to grant wishes. The Pi’illo folk were protecting the stones from misuse. Then the Bat King, Antasma, came to steal the Dark Stone to fulfill his desires. The Pi’illo could not defeat him, though managed to trap him in the Dream World, however Antasma was able to destroy the Dark Stone at the last second, thus causing the Pi’illos souls to be trapped in Nightmare chunks upon being hit by one, thus rendering them helpless. Prince Dreambert, in a haste to save his fellow people then runs out, the Bros. following him. After catching up to Prince Dreambert and saving some Pi’illos they learn from one in particular that Eldream, a Pi’illo elder, knows how to reach Dream’s Deep. The Bros. then set off to find him in Mushrise Park. Upon arriving at Mushrise Park the Bros. learn that Brickle, the Manager of the park, has Eldream but will not give him up unless they catch him. After the Bros. chase him, gaining hammers during their attempts, they find him on top of a fountain, where he tries to flee but gets stuck in the fountain top. The Bros., going underground, turn up the water pressure causing the fountain to explode, and freeing Brickle. Meanwhile at Brickle’s Maintenance hut, Grobot, the hydrozation robot, gets hit by a large piece of the fountain, damaging it and causing it to go haywire. Brickle thanks the Bros. and tells them they can use his bed in his hut. Upon arriving there, Grobot is incredibly unstable and attacks Brickle. It then attacks the Bros. After defeating Grobot, Brickle is heartbroken although quickly gets over it and allows the Bros. to use his bed to free Eldream. In Dreamy Mushrise Park the Bros. encounter Dreambunny, Eldream’s pet rabbit, who’s carrying the nightmare chunk containing Eldream. Dreamy Brickle interrupts them though saying the rabbit is what will bring people to his park and competes with the Bros. for it. After Mario and Luigi corner Dreambunny, it gives up the Nightmare Chunk, allowing the Bros. to free Eldream. Eldream opens a portal to Dream’s Deep with the use of Dreambunny and then goes to spend some time with his pet. The Bros. enter said portal and proceed to Dream’s Deep. The Bros. quickly corner Antasma but are held back by his obnoxious screeching. Meanwhile in the real world, Starlow is watching Luigi when Kamek appears along with Private Goomp, Corporal Paraplonk and Sergeant Guy, all three now promoted to royal guard. Bowser then enters, demanding the location of Peach, and upon catching the princess’s scent, jumps into the Dream Portal. He arrives in Dream’s Deep right where the Bros. are confronting Antasma. Upon being convinced by Antasma and his claims of new moves and such, Bowser fights with Antasma against the Bros. After being beaten by the Bros., Antasma increases Bowser’s power and floors Mario, Luigi and Peach. Antasma then flees with Bowser, stating they will get Peach later as they have work to do. Eldream who arrives on the scene, helps get the Bros. and Peach back to the Real World. Back in the Real World, the Bros. learn that Antasma is going after the Dream Stone, which resides in Dozing Sands. Upon reaching Dozing Sands, the Bros. meet Britta, a ruthless construction manager who says she can’t help them as there is no more treasure in the already explored areas besides the path with the large sand slide. The Bros. learn that to get up the sand slide they have to find the four Deco Pi’illos of the Dozites, special stones that fit into Zeekeeper statues, when all collected would allow them to proceed up the sand slide. After finding three of the Dozites, the drill monster, Torkscrew eats the fourth Deco Pi’illo, resulting in a chase on the Drilldigger. Upon drilling it several times in a chase, it coughs up the Deco Pi’illo, who, like the others, was trapped in a nightmare chunk. After placing the last Dozite in the last statue, the sand slide becomes climbable and Britta races ahead of the Bros. to the newly accessible area in hopes of treasure. Upon reaching the new area Torkscrew attacks Britta and swallows her. After beating Torkscrew to the point of which it explodes, Britta is freed, however fades in and out of consciousness in a bad state and is carried off for medical attention. The Bros. approach the ruins that hold the Dream Stone to discover Antasma and Bowser had already stolen it. Prince Dreambert realizes that the Dream Stone’s alter is a Dreampoint, a point where one can enter the Dream World easily. Prince Dreambert suggests that the Bros. try to find the Dream Stone Soul who may be able to tell them where Antasma and Bowser went with the stone. Upon hearing this, Mario enters the Dream World as Luigi sleeps on Prince Dreambert on the Dreampoint, into Dreamy Dozing Sands. After finding the Dream Stone’s Soul, it tries to hide as it doesn’t want to get involved but is pestered to the point it is consumed by fury, turning into the massive Robo-Drilldigger to get rid of the Bros.. Dreamy Luigi, fusing with many Luiginoids, then becomes Giant Luigi to defeat Robo-Drilldigger. After doing so, the Dream Stone’s Soul tells Luigi where the Dream Stone was taking, Mount Pajamaja. To reach Mount Pajamaja, the Bros. need to take a tour there, signing up requiring them to go to Wakeport. At Wakeport, the Bros. run into Kylie Koopa, who doesn’t remember them yet offers them some optional work at her office, and Popple who just robbed a building in broad daylight, who remembers but doesn’t recognize the Bros. Upon signing up for the tour and arriving, everyone who signed up but the Bros. flee in fear before the tour even starts. Mario and Luigi learn from one of the two tour guides, Lil’ Massif, that the tour can’t start unless Big Massif, his older brother and the other tour guide, shows up. During their search, the Bros. help a Hooskin make a proposal, gaining some items upon doing so and learning of a hint to Big Massif’s location. The Bros. later find Big Massif voluntarily asleep on a Dreampoint. Luigi then falls asleep in an attempt to connect to Big Massif’s dream to wake him up. The Bros. succeed in both that and in entering Dreamy Wakeport, but discover that to meet Dreamy Big Massif they have to beat his four apprentices with special conditions involved. After beating all four, it is revealed that Dreamy Big Massif was disguised as the Referee. Upon beating Dreamy Big Massif, Big Massif wakes up, notices he slept in and starts the tour to and up Mount Pajamaja. After climbing up to the summit of Mount Pajamaja, the group comes across the mammoth guardian of the mountain, Mammoshka, who is currently sleeping. The Massif’s get by unnoticed but Luigi sneezes, waking up Mammoshka, who gets enraged when it sees the Bros. After beating the Guardian, the Bros. proceed to the summit where they find Antasma, Bowser, Kamek, Private Goomp, Corporal Paraplonk and Sergent Guy with four large speakers. It is revealed that the Dream Stone needs to charge before it can grant wishes. Private Goomp then turns on the speakers and music known as the Dreambeats starts playing, making all who hear it fall asleep, except for Pi’illos, Starlow, Antasma and Bowser (who is covering his ears). The Bros. try to escape but Luigi falls asleep while Mario fights the drowsiness. Prince Dreambert suggests going to the Dream World to escape the music until it’s over upon stumbling upon one in their escape. Mario manages to escape the Dreambeats by diving through the Dream Portal of a nearby Dreampoint into Dreamy Mount Pajamaja, but the Dream Portal soon closes as the music has made Luigi so deep in his sleep that it can’t remain stable. Meanwhile, the entire island falls asleep and Dream Orbs, orbs created by those who sleep, are absorbed into the Dream Stone to power it. Mario suggests to cause a eruption in the Dream World’s volcano to stir Luigi awake to re-open the Dream Portal. Upon reaching the summit, the Bros. discover the dream version of the mountain volcano, Mt. Pajamaja, is alive and anger it by popping a pimple on its nose. Mt. Pajamaja’s reaction sends the Bros. running back to where the Dream Portal was but it hadn’t re-appeared yet, leaving the Bros. to face Mt. Pajamaja, resulting in another Giant Luigi battle. After beating the Volcano, the Dream Portal reappears and Mario returns to the real world. Starlow and Prince Dreambert discuss their next plan of action and decide to hide Princess Peach as that would be Bowser’s prime target and head back to Pi’illo Castle. At the crater of Mount Pajamaja the Dream Stone is finished charging and Antasma makes the first wish. Antasma wishes for a Castle for him and Bowser, one that is impenetrable and also one that is feared, and a large castle, a mix between Bowser’s and Antasma’s designs, comes out of the Dream Stone and floats into the sky. Antasma then tries out the castle and destroys several small islands around Pi’illo island with large lasers. Then a large impenetrable shield surrounds the castle. Bowser dubs this castle Neo Bowser Castle. Antasma then offers Bowser the next wish. When the Bros. arrive at Pi’illo Castle, they find everyone in panic and soon learn what the first wish was for. They decide to find Princess Peach and protect her and find out she’s at Driftwood Shore. When they arrive, they are told to go see Broque Madame who has disguised Peach and Toadsworth as Block folk. It is suggested that Peach should be hidden in the Dream World from Bowser. The Bros. meet Popple again who is on a tour but still can’t find anything worth stealing. After that the Bros. find a Dreampoint and they meet Seadric, a Seadring that would be glad to help hide Peach. It is suggested though that Peach should be held deeper in this Dream World and Seadric suggests the use of Dream Eggs to expand the world. Seadric then tells the Bros. to go see his two brothers and one sister to get their three Dream Eggs. After doing so, Seadric expands the world and then tells the Bros. to meet him in the next area after finding the prizes he left for them. After meeting up, the Bros. asked why he left monsters, with Seadric replying that monsters shouldn’t be here and that something bad got in. After the final expansion and hiding Peach in the deepest part. It is revealed that Peach was actually Kamek in disguise, along with the royal guard, Private Goomp, Corporal Paraplonk and Sergant Guy, and it’s revealed they already had Peach. The royal guard then battles the Bros. and reveal they can only be beaten if all of them are KO’d at once. After doing so, they are demoted to janitors and teleported out by Kamek who then leaves. The Bros. start looking for a way to get to Neo Bowser Castle when they discover Dr. Snoozemore has returned and go to see him. Upon finding him in the collection room of Pi’illo Castle, he is startled to see a living Pi’illo. He suggest trying to find the Zeekeeper to break the shield around the Castle. Prince Dreambert remembers seeing a Zeekeeper statue in Dream’s Deep in Pi’illo Castle. The statue would’ve allowed the Bros. to find the Zeekeeper’s location but to their dismay, it is deactivated. Upon reactivating it, Mario and Luigi learn to summon the Zeekeeper, they must use the Ultibed, which in order to access, must first be built by a Bedsmith once they collect the five Zee Parts scattered across the island. The Bros. have little trouble getting the parts, but upon finding the Jelly Sheets, a group of Fly Guy Rs steal it. The Bros. locate the group taking a break on the path towards the Blimport. Mario devices a plan to steal the sheets back. While the Bros. sneak by, Starlow and Prince Dreambert have a loud conversation about a rumour of Bowser having a birthmark in a certain place in a certain shape. The Fly Guy Rs get interested and distracted allowing the Bros. to steal it back before having to fight the Fly Guy Rs. After collecting the necessary parts the Bros. head to Wakeport and run into Popple again, who is trying to steal from Pi’illo-per’s, a Pi’illo artifact collector, collection room. The Bros. follow Popple to a sealed-off area full of ruins. Popple mistakes a Wiggler called Wiggly for a security guard. When the Bros. walk past Popple, he pulls them to one side and still doesn’t remember them. He then tricks the Bros. into helping him fight Wiggly, by talking first, and then after insulting Wiggly, fighting him. Popple causes problems to the Bros. during the battle by enraging Wiggly, preventing a Bro from dodging or saving his own skin. After Wiggly is defeated he turns on the Bros. immediately but is beaten. Upon learning that Wiggly wasn’t a security guard, he insults Wiggly again, getting chased, and claiming he’s had enough of the island. The Bros. then find Pi’illoper who is amazed at the Bros. Pi’illo artifacts and takes them to his prize possession, Bedsmith, who is trapped in a Nightmare Chunk. When the Bros. finally reach the Nightmare Chunk, Earthwake, the guardian holding the nightmare chunk in its head, activates and forms a robot made of buildings resulting in another Giant Luigi battle. After beating Earthwake and breaking the nightmare chunk, Bedsmith is more than happy to help, but needs to meet the Bros. at his workshop in Somnom Woods to build the Ultibed. After arriving in Somnom Woods, Bedsmith makes the Ultibed, and then tells the Bros. to find the Zeekeeper they would have to sleep in the temple in Somnom Woods. To reach the temple, the Bros. have to free the Pi’illo Masters which hold the keys to reaching the temple. Mario and Luigi, however slightly slowed by the antics of the Nommons, manage to save all six of the Pi’illo Masters and are able to continue towards the temple. Unfortunately, upon reaching the ideal spot for the Ultibed to be slept on, the temple’s defence system releases the guardian, Pi’illodium, who then attacks the Bros. After defeating the guardian, the Bros. then place the Ultibed into position, and Mario enters Dreamy Somnom Woods to find the Zeekeeper. Climbing up the large tree towards where the Zeekeeper sleeps, Mario and Luigi survive several of the tree’s confusing tricks and make it to the top, where they find a large rainbow egg (known as the Zee Egg) of which Mario smashes, releasing the Zeekeeper who instantly attacks the Bros., this soon triggering another Giant Luigi battle. After the Zeekeeper is defeated, he notices Prince Dreambert with the Bros. and reverts to his usual casual demeanour, no longer hostile. Upon hearing the dire situation, the Zeekeeper agrees to help after being promised (against Mario’s will) that after Antasma’s defeat he would get every single coin Mario has, takes Mario out of the Dream World and then proceeds to scope out Neo Bowser Castle, once doing so returns near the forest entrance, awaiting the Bros. to shatter the barrier. Once they board the Zeekeeper and he flies near the castle, he unleashes the Wakebeam upon the castle, shattering the barrier and causing the castle to plummet in an empty area slightly to the north of where the forest entrance is, right between Mt. Pajamaja and Somnom Woods. The Zeekeeper lands with the Bros., and then rests, allowing Mario and Luigi to then storm the castle once prepared after a shopkeeper rushes by to set up shop near the castle to reap much cash from desperate shoppers. Upon infiltrating Neo Bowser Castle, Kamek casts a spell on the rooms and passages, making it harder for the Bros. to navigate the castle. Upon doing so, Kamek and Antasma flee into the Dream World through a platform behind a sturdy fence. Mario and Luigi soon figure out the tricky navigation, and eventually are able to chase after the duo into Dreamy Neo Bowser Castle. After hunting down Kamek, they do battle with him, however Kamek exits the battle midway in order to flee to another Dream World, releasing the spell on the areas in Neo Bowser Castle and leaving. Mario and Luigi follow suit and re-enter Neo Bowser Castle, and proceed deeper. Meanwhile, upon Bowser stating his desire to conquer the world now, Antasma suggests Bowser sleeps due to his potential dream energy being raw and powerful. Bowser agrees to this line of logic, and goes along with the suggestion. Mario and Luigi after continuing through, find Kamek who casts a similar spell as before on to the nearby rooms, making navigation tricky. Antasma appears and once again opens the Dream Portal, the evil duo entering again from a similar fenced off platform. Upon Mario and Luigi once again maneuvering the tricky corridors of this next area and setting the wind turbines to blow the huge rolling Bob-ombs over a gap in their track and on to the switch removing the gate fence, they return to the platform and re-enter the Dream World. After escaping the rising lava, the Bros. find Kamek disguised as Peach, however do not fall for it this time, causing Kamek to drop the act and engage battle with them yet again. Deep into battle, Kamek once again exits the duel along with the Dream World, heading deeper into the castle yet again, causing the Bros. to follow. Mario and Luigi quickly catch up to Kamek, startling him as he was in the middle of muddling up the rooms. He flees through another Dream Portal, as like before. The Bros. adapt to this area’s emphasis on large rolling Bob-ombs, and manage to lower the gate blocking the platform Luigi would then sleep on. Mario enters the Dream World, and eventually finds Kamek who takes the Bros. head-on this time. After a rough battle, Kamek is defeated soundly, and the magic departs from the Real World, allowing Mario and Luigi to continue upon their leave of the Dream World. The battered Kamek then decides to use the rest of his magic to assist Bowser, and disappears. Mario and Luigi are once again stopped from their trek deeper into the castle quite soon by several intense flames being shot out of three Dream Worlds, and then realize they must enter each of the Dream Worlds and stop whatever is causing the flames. Upon succeeding in doing so, Mario and Luigi enter the doorway at the end to find Bowser sleeping on Antasma as a pillow with a barrier protecting him. Prince Dreambert states that the strange purple vines they’ve seen everywhere throughout the castle are what powers the building, and that they originate from Antasma. Luigi suggests they enter Bowser’s Dream World, Prince Dreambert realizing they could try what they did with Big Massif with Bowser. Prince Dreambert connects himself to the vines as pillow form, and Luigi sleeps on him, Mario entering the Dream World. After traversing the Bowser-infested Dream World, the Bros. soon come across Bowser gulping down chunks of meat. Bowser spots Mario and Luigi, and orders to have more meat served to power him up, finishing all the meat, and entering a rage upon finding that out. He starts inhaling the area around him, growing in size just like when he ate the meat. Bowser then jumps off the ground and into a pit in what seems to be a fatal fall. Mario and Luigi run over to where Bowser jumped, and look down in the pit. They see no sign of Bowser, and assume he’s been dealt with. Mario and Luigi try to move, but they are knocked back by a Giant Bowser wrecking the place up, clearly unharmed. Luigi signals Mario that they’re going to do what they normally do in this situation, a Giant Battle. The real Luigi confidently signals Starlow, and a Giant Battle commences. Upon Bowser getting struck by Finishing Bros., Mario and Luigi celebrate, only for Kamek and some Magikoopas to appear and power Bowser up, causing the Giant Battle to continue. When Luigi manages to make Bowser woozy and open to damage, the Bros. start up Star Driver, another version of Finishing Bros. where Prince Dreambert powers up the star instead. With this attack being successful, the Bros. defeat Giant Bowser. Mario and Luigi leave the Dream World and after pursuing the evil duo, discover that Bowser was planning to double-cross Antasma all along. Antasma reveals he had made a wish on the Dream Stone for the ability to create Dream Portals at some point, and flees from Bowser through one. Bowser, meanwhile, flees himself with a Paratroopa holding Princess Peach. Prince Dreambert decides to fight Antasma just as he did centuries ago, and loses. Mario decides to avenge him and jumps into the Dream Portal himself. Dreamy Luigi and a barely conscious Prince Dreambert join in the fight to assist him. After Mario defeats Antasma for good, they leave the Dream World, knowing they still have Bowser to take care of. Narrowly avoiding Private Goomp, Sergeant Guy, and Corporal Paraplonk’s Bob-omb attacks, Mario, Luigi, Starlow, and Prince Dreambert make it to the castle balcony, where Bowser and Peach await. Bowser boasts about the power he now has, with the Dream Stone and Peach in hand. Suddenly, Peach and Starlow activate their wish power from the previous game and, at the request of Prince Dreambert, destroy the Dream Stone. Bowser is initially shocked about this, but then screams in rage, “NOT YET!” as he inhales the Dream Stone’s pieces and becomes a form known only as Dreamy Bowser. Mario and Luigi engage battle with him, and upon winning, knock him flying into the sky. Suddenly, without the Dream Stone to maintain it, the castle begins to crumble, but the Zeekeeper gives Mario and friends a lift back to Pi’illo Castle just in time. Back at the castle, Toadsworth is so relieved to see the princess. Prince Dreambert presents the Zeekeeper with the Dream Stone’s essence extracted from Bowser’s body, hoping to get it repaired. He does so, but it becomes the Dream Coin, which spouts infinite coins, instead. The Zeekeeper explains that he made it this way because simply having the power to grant all wishes is too risky, and it’s more intuitive to “buy” one’s wishes. Prince Dreambert, seemingly shocked at what Zeekeeper was doing, pouts at the sight of the concoction, but Broque Monsieur says it’d be a great attraction, and Mario, Luigi, and Peach agree. Meanwhile, Bowser and his minions are desperately trying to escape the island in the Koopa Clown Car, and Bowser announces he will come back for revenge, finally remembering Luigi’s name. They are then showered in coins from the Dream Coin, Private Goomp and Sergeant Guy rock the Koopa clown car so much, trying to get coins, that it falls into the ocean. The group then start their vacation, shown during the end credits.