This summertime comedy from last year tries to plug-in to the “coming of age” meme that sends adults back to the time, when they were young, that will be remembered, fondly, for the feelings and experiences they think actually happened, and wish they could experience all over again, even though, at the time, they destroyed countless pillow cases with their teeth while they hurled muffled screams into the darkness.

Oops, sorry! Seems I got carried away a little. Actually, TWWB deserves a review less distorted by this critic’s painful past because there’s some genuine skill and solid entertainment to be had, even if all of the parts don’t quite fit together.

The kid coming of age here is Duncan (Liam James), 14, who goes on vacation near Cape Cod with his mother, Pam (Toni Collette), and her boyfriend, Trent (Steve Carell) and his daughter, Steph (Zoe Levin). Their neighbors are hard-partying types, especially Betty (Allison Janney), who has a daughter about Duncan’s age. We see early on that Duncan hates Trent, who is a surly and malicious type, although Pam tries to smooth things between the two, with no success.

Duncan relieves the tension by hanging out at Water Wizz, a theme park whose main attraction is a large water slide. The manager, Owen (Sam Rockwell), has sympathy for the troubled, quiet Duncan, and is able to get him out of his protective shell with his easy-going, slacker attitude. Duncan takes a job there, and develops confidence in himself, which, ironically, makes him defy Trent even more.

The conflict leads to an explosive public confrontation at a party one night when Duncan accuses Trent, correctly, of having an affair with a beautiful neighbor (Amanda Peet). Pam is humiliated and torn, but she decides to stay with Trent. In an effort to save their relationship, Pam and Trent decide to cut the vacation short. Duncan is devastated because he will have to part with Owen, who has become a father-surrogate for him.

The film concludes, uneasily, with not one but two discordant endings. In the first, just as the family is leaving, Duncan breaks free and runs to Water Wizz, with Pam and Trent running after. He embraces Owen and, in a symbolic rite of his independence, teams with him in a dangerous, and unprecedented stunt on the water slide, to rapturous applause from the crowd. Then, in the second ending, as Trent drives the family away, Pam moves away from him to sit next to her son in the back seat, as if silently announcing that the relationship is over.

That second ending leaves a sour taste that pervades the whole film. I don’t think first-time director-writer team Nat Faxon and Jim Rash ever resolved this right through the final script. Steve Carell’s performance is wildly off-base, and it darkens the tone of the film whenever he’s onscreen. If he wanted to show he has the chops for Ibsen and O’Neill, he succeeded. He makes Trent a very unpleasant but still fascinating man, and the dynamics of his relationship with Duncan could make for a sturdy, dark drama, like This Boy’s Life. Unfortunately, that second ending seems more of a lead-in to the real and unseen climax of the film, one which is likely to be violent and end up in Juvenile Court.