‘Simple Favor’ spins a deliciously campy thriller

Comedy director Paul Feig tries a thriller on for size with the juicy “A Simple Favor,” a suburban Connecticut murder mystery that’s “Gone Girl” meets “The Stepford Wives.”

The consciously campy “A Simple Favor” is as bright and bracing as an ice cold gin martini with a lemon twist and just as satisfying.

Anna Kendrick stars as Stephanie, a mommy vlogger raising her son, Miles (Joshua Satine), on her own after her husband’s tragic death in a car accident. Shunned by the other parents (a gloriously catty trio played by Andrew Rannells, Aparna Nancherla and Kelly McCormack), she takes up with the glamorous, elusive and mysterious Emily Nelson (Blake Lively), mostly because their kids want a playdate. Thirsty for attention, she agrees to slurp down afternoon martinis.

As the sexy, stylish Emily, Ms. Lively is at her best. The role offers her a chance to try on a deliciously naughty performance while playing on her flair for fashion. Decked from head to toe in threepiece suits, Emily cuts a seductive and serpentine figure. She snares Stephanie into her web the same way she snagged her husband, the dashing novelist Sean (Henry Golding), with a potent mixture of sensuality and secrets.

Ms. Kendrick’s schtick — her self-consciously dorky rapid-fire delivery — has started to wear thin, but in “A Simple Favor” it suits her character perfectly as the ever-chipper, can-do Stephanie, who has a penchant for Peter Pan collars and pompoms. When Emily goes missing, leaving her son Nicky in the care of Stephanie, her new best friend of a few weeks, she pours all her energy into caring for Emily’s family and searching for her missing friend. When it comes to solving mysteries, leave it to a mom. Stephanie is the ultimate uber-organized Nosy Nellie perfect for the job.

“A Simple Favor” is about as deep as a champagne coupe, but the performers, slick execution and pop-art style make it a delightfully fun and kitschy ride.