Greta Gerwig (right) and Ethan Hawke appear in a seen from "Maggie's Plan."

“Maggie’s Plan” is the kind of film that could have been a disaster if it had fallen into the wrong hands.

Fortunately, director/co-writer Rebecca Miller has a cast that helps keep it all together – led by Greta Gerwig. Every time the film feels like it is going to get too cynical, Gerwig’s charm reels it back in – making “Maggie’s Plan” a pleasant diversion in a sea of summer blockbusters.

Gerwig plays the title character Maggie, who is ready to start motherhood without the fuss of a relationship. Her plans for artificial insemination go awry however when she falls for a smart scholastic married man named John (Ethan Hawke).

He’s trying to break free from his wife Georgette (Julianne Moore) and the affair blossoms into something else.

Three years later Maggie has her child and a husband, but starts to fall out of love with John – hatching a plan to get him back together with Georgette.

Miller’s film has plenty of similarities to a Woody Allen film, including a New York setting, a strong cast, and some crackling dialogue that requires the audience to think while they laugh.

Gerwig is the perfect choice for the material, an actress who conveys a wittiness that always seems like she is one or two steps ahead of everyone else in the room – even when she is one or two steps behind.

Moore has a lot of fun in her role, chewing up the scenery with an over the top European accent. Hawke manages to not make the audience totally hate John – even though the character’s flaws and insecurities make him easily unlikable.

There is also a couple of nice moments with “Saturday Night Live”alum Bill Hader and Maya Rudolph playing a couple that is friends with Maggie.

“Maggie’s Plan” doesn’t have quite the same sharpness as some of Gerwig’s other recent films like “Frances Ha” and “Mistress America,” but it still has pretty astute and cynical eye about relationships – building to a final shot that brings it all together quite nicely.

Starring: Greta Gerwig, Ethan Hawke

Directed by: Rebecca Miller

Rating: R for language and some sexuality

Playing at: Regal Green Hills Stadium 16 in Nashville (Opens Friday)

Grade: B