For the vast majority of its runtime, A Simple Favor performs a wonderful balancing act with its tones. The film is a mystery/thriller in the vein of Gone Girl, but it is also a comedy. Those two things really should not mix, but somehow DIrector Paul Feig does it. There are genuine laughs throughout that don’t completely puncture the building tension of the mystery. Then it gets to the end and it all falls apart. Fortunately, the rest of the movie is so good that it is easy to forgive its disappointing ending.

A Simple Favor star Anna Kendrick as Stephanie Smothers, an overprotective single mother who runs a mommy vlog. She strikes up a friendship with Blake Lively’s Emily Nelson, a mother of friend of her child and a high powered executive. Their friendship grows, but soon Emily disappears. This sets off a mystery of what happened to Emily and who exactly Emily was. Both Stephanie and Emily’s husband are suspected.

Initially, the movie does an excellent job of balancing tones, setting up a thriller while also being very funny. That mix of tones also helps develop the friendship between Stephanie and Emily. Without the humor, Emily is an expressly terrible person. She is mean to her kid and husband, she drinks a lot and is frequently just awful. It is played as a joke, and it works, contrasting the uptight Kendrick with the relaxed Lively is delightful. You can see how the lonely Stephanie is taken in by the delightfully awful Emily. It keeps balancing the tones as Stephanie begins to investigate the disappearance. It manages to keep the humor present without completely puncturing the tension.

This sort of thriller, like Gone Girl, tends to not have a lot of place for humor. It naturally lessens the tension that the movie is trying to build. Here, largely by keeping the humor closely related to the characters and not the mystery itself, the movie manages to have its cake and eat it too. At least, it does until the final act. The tension builds through Stephanie’s searching and all the inconsistencies that she finds in Emily’s history and story. But the final revelations alternate between disappointing and laughable. It ends up in complete comedy territory, but it stops being funny. Instead of the character based humor from the start, it relies on slapstick and stupidities. It just doesn’t work.

The ending is undoubtedly disappointing, but that mostly serves to highlight how brightly the rest of the movie shines. Anna Kendrick is delightful as the perky and occasionally sad center of the movie. Blake Lively is perfect as Emily, the only problem is that the structure of the movie keeps her off screen for the bulk of the movie. There is good, real stuff with how the characters deal with loss. Ending notwithstanding, A Simple Favor is a fun, entertaining movie that is well worth seeing.

****