HBO star's 'Shot in the Dark' finds its target

In 1999, when he was 22, Adrian Grenier set out to find his absentee father. The actor, now known as the movie star in HBO's "Entourage," also decided to film his search and shape it into a documentary. Tomorrow night at 10:30, following the third-season finale of "Entourage," HBO is airing the highly personal film, called "Shot in the Dark." (Don't worry; the fourth season of "Entourage" begins on June 17.)

In all likelihood, HBO would not be featuring "Shot in the Dark," which was completed in 2002, if Grenier weren't one of its stars. But, that said, the movie is an engaging piece of work in its own right, a heartfelt and intimate portrait of a young man needing to look backward before he can move forward.

Grenier had a few visits with his father, John Dunbar of Ohio, until he was 5. After that, he was raised solely by his mother, Karesse , in New York: "I was your mother and your father," she tells him on camera.

But the plot thickens as "Shot in the Dark" proceeds. Like a segment of "This American Life" on NPR, the full story unfolds gradually and plays with our sympathies as each new piece of information is revealed. The movie isn't about a mother left holding the baby after the father splits, as it may seem early on. In fact, Karesse dumped Dunbar, whom she knew briefly at a commune in the 1970s. And then further complications arrived in the form of Dunbar's wife, Debbie, who is deeply threatened by Grenier and doesn't encourage visitation. By the time we've met all the people involved -- the profoundly passive Dunbar, Dunbar's sweet-as-pie parents, Debbie, and others -- the movie has evolved into a layered family portrait.

Grenier seems to change in the course of "Shot in the Dark." At first, he is cynical and unwilling to take his journey seriously. When he tells a therapist he is naming his movie "Shot in the Dark" "because that's all I am," he laughs too hard, unaware of the pain behind his joke. He is also as passive as his father, despite the fact that, in 1999, he'd already made headway in the movies, and despite the fact that he was making "Shot in the Dark" in the first place.

But once he has reconnected with his father and that side of his family, and once his history has become less about abandonment and more about the intertwining of individuals and their issues, Grenier appears more grounded. The meaning of his search, and his movie, come into focus. It's a subtle shift in his mien, but it's nonetheless clear.

"Shot in the Dark" doesn't err on the side of self-indulgence; Grenier keeps his narrative trained only on those events and interviews that relate to his search for his father. He doesn't mention his career. Yet he unnecessarily fills the front of the film with man-on-the-street interviews about fatherhood, as if to guard against self-indulgence. The interviews are supposed to get at the meaning of fatherhood, but they are uninterestingly empty, and they only clog up the opening minutes. Once "Shot in the Dark" gets on track, though, it shows us exactly what those interviewees fail to describe.

Matthew Gilbert can be reached at gilbert@globe.com. For more on TV, visit boston.com/ae/tv/blog/.