“The Way, Way Back” writers Nat Faxon and Jim Rash are the two Academy Award winning screenwriters who co-wrote, with Alexander Payne, George Clooney’s wonderful “The Descendants.” This gave them the power to go forth and give us for our viewing pleasure, “The Way, Way Back,” a coming-of-age summer movie about Duncan, a 14-year-old New York boy lost in the miasma of uncertainty, bewilderment and adolescent angst of the smartphone age.

Duncan, (Liam James, “The Killing”) as we open, is slumped in the rear, turned-around seat of a 1970 Buick Estate wagon, heading towards Massachusetts and the summer camp of Trent (Steve Carell), his mother’s boyfriend.

Mother Pam, asleep in the front seat, is the always wonderful Toni Collette. Pam is divorced and middle aged, with all of the terror that goes with that.

Boyfriend Trent is at the wheel while his spoiled, mean-girl teen daughter Steph (Zoe Levin) sleeps in the second row.

Carell sheds his trademark comedy suit to play a philandering, over-bearing jerk. The part is front loaded, so that you will hate Trent from the moment he opens his mouth. He keeps chiding poor Duncan about making “their new relationship work,” while it’s already clear that it’s doomed. Duncan, even at 14, has a gentle soul. Trent is a burned-out cynic.

The story is Duncan’s, who despises Trent even more than you will. But it’s hard to feel too sorry for Duncan, as he does little more than sit on stoops, sulk and shrug.

Arriving at the summer home, the movie picks up a bit when Trent’s longtime neighbor, Betty (Allison Janney) trots out on the porch with her third margarita, and welcomes the crowd. Betty is a boozer and never shuts up, her only saving grace is she has a sweet, but naturally cynical late-teen daughter, Susanna (Anna-Sophia Robb.) She and Duncan make eye contact, and we hope for the best.

The summer will explode on the Fourth of July and continue with party after party with local pals Kip and Joan, played by Rob Corddry and Amanda Peet. It’s clear that this foursome, so bored with their lives, indulge in this annual bacchanalian beach blanket sex bingo, before they go back to Manhattan and continue dying. We’ve seen this story before written by better writers.

The boredom of the cardboard character adults sends our Duncan off into the village on a borrowed girl’s bike to find some joy. We hope he does, because this crowd wears on us early on.

The joy, at least for us, comes when Duncan discovers “Water Wizz,” a seedy water park with fried dough stands, electric games and soda machines, where the boozing adults drop their kids, while they sleep off the partying.

Water Wizz is manned by Owen (the wonderful Sam Rockwell) a big city dropout. Owen runs the park, filled with hundreds of half naked teenage girls and overweight horny boys, and is having a sort of fourth summer romance with the boss, SNL’s old favorite Maya Rudolph.

It’s possible that Owen’s a divorced ex-ad writer or sports car salesman whose wife threw him out. Now he’s having a second childhood while desperately holding onto his 40s and hoping a second chance will find him.

We love Sam Rockwell, even in this thin and undeveloped part. Sam is so enjoyable that when he’s off screen, we wait for him to come back and turn back on the lights.

Owen meets Duncan and a better part of the movie appears. Here the older lost boy sees his younger self in the kid. He senses the boy’s pain and shines to him. He gives him a staff T-shirt and part-time gig. Life opens up for Duncan like a beach umbrella. With Owen and the other adults (writers Faxon and Rash beautifully play two of the operators) Duncan discovers grownups who accept him as he is, a kid looking for summer fun, for love and acceptance.

At a night-time marshmallow roast, sexy Peet plays a game with Trent in the shadows, while the others are roasting s’mores. When it all explodes, Duncan and Trent collide, the others shrink off and the summer comes to an end. Bags and damaged hearts and egos are packed back into the estate wagon. It’s not the ending we hoped for, Mama dumping Trent and marrying Owen and sailing off for the islands, but there are glimmers of light. Duncan has been to Pinocchio’s island of lost children, with Owen as his Jiminy Cricket. We know he will be back.

“The Way, Way Back,” is more a soft-serve chocolate cone than a summer lobster roll sandwich, but the cast is worth the trip.

J.P. Devine is a former stage and screen actor.