'A Simple Favor'

Comedies and thrillers, if you think about it, are polar opposites as movie genres. Thrillers require tight control so the tension can build second by second, while comedies need to be loose so the laughs can flow.

The fact that director Paul Feig, a comedy guy, manages to do both at once in the light-fingered but dark-hearted “A Simple Favor” is kind of a big deal. 

Stephanie Smothers (played by Anna Kendrick) is a single suburban mom and a vlogger imparting zucchini chocolate-chip cookie recipes and instructions for friendship bracelets. One day when picking up her son Miles (Joshua Satine), the boy wants to have a playdate with his schoolmate Nicky (Ian Ho) — which is how Stephanie meets Nicky’s mom, Emily Nelson (Blake Lively), a stylish PR executive for a New York fashion label. 

Emily says sure, and while the kids play upstairs, Emily and Stephanie become fast friends, sharing intimate conversation over martinis. The party only stops when Emily’s husband Sean Townsend (played by “Crazy Rich Asians” hunk-of-the-moment Henry Golding) shows up and starts making out with Emily.

After a few more playdates, Emily calls Stephanie to ask for a favor: To take Nicky after school while she deals with a work emergency. An afternoon turns into an evening, then another day, and soon Stephanie is concerned that something has happened to her new best friend.

That’s where the synopsis stops, because part of the fun is how Feig and screenwriter Jessica Sharzer (adapting Darcey Bell’s mystery novel) tease out the suspense behind every plot twist. Suffice it to say that when Stephanie starts playing Nancy Drew, she discovers everybody has something to hide — even herself.

Feig deploys Kendrick and Lively perfectly, first as a strong comedy duo and eventually as sexy and smart figures on their own. No male director working handles women characters as intelligently as Feig — examples include “Bridesmaids,” “Spy” and even his “Ghostbusters” reboot. Here he gives Kendrick room to run her perky persona into some dark places, and discovers in Lively a funny side she hasn’t shown in her movies (but she has in tweets teasing hubby Ryan Reynolds).

In the end, “A Simple Favor” is like one of Emily’s martinis: A strong kick that makes you giggle, ice-cold delivery, and a twist that gives it plenty of bite.

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‘A Simple Favor’

★★★1/2

Opens Friday, Sept. 14, in theaters everywhere. Rated R for sexual content and language throughout, some graphic nude images, drug use and violence. 117 minutes.