In [*Knives Out*](https://slate.com/culture/2019/11/knives-out-movie-review-rian-johnson-trump-immigration.html), the new whodunnit from Rian Johnson, one suspect possesses what the loquacious detective Benoit Blanc (Daniel Craig) calls “a regurgitative reaction to mistruthing.” To put it in simpler terms: Whenever Marta (Ana de Armas) tells a lie, she pukes. (Those prone to sympathy gagging will perhaps be relieved to know the actress simply used [baby food](https://www.hollywoodreporter.com/news/making-knives-how-rian-johnson-assembled-a-star-studded-jigsaw-puzzle-1253787).) We won’t give away the answer to the movie’s big mystery, but for us this represented a smaller one: Is this a real medical condition or just a convenient plot device?