Blake Lively turns deadly in Paul Feig’s 2018 incest comedy. And if you’re thinking “but incest isn’t funny,” in this case you’d be right.

The incest subplot also has no relevance to the central mystery of what happened to Emily (Lively), a glamorous mum who asks the eager Stephanie (Anna Kendrick) to pick her son up from school one day and swiftly disappears. It’s basically David Fincher’s Gone Girl as directed by Feig, a man who looks too much like Michael Gove to be trusted and tries (and fails) to make kitsch comedy from a story involving child abuse and drug addiction.

Most twisty thrillers have a nonsensical element or two, but there’s not a single plot point, character or line of dialogue in A Simple Favor that makes a lick of sense. “Poisoning isn’t my style,” says Stephanie, “I don’t even eat gluten.” Feig’s attempts to distract from the nonsense include a French pop soundtrack and a vlog exposition device, where Stephanie regularly broadcasts the intimate details of a sensitive missing persons case.

The whole thing is about as shallow as The Shallows and as convincing as Prince Andrew, more confused than confounding and more grating than ingratiating. The decision to make Stephanie so annoying and unsympathetic is as infuriating as watching her rap, an embarrassing hallmark of writer Jessica Sharzer who had Emma Roberts do the same in Nerve. And Kendrick is no more Kendrick than Feig is Fincher.