“Lamb” opens Friday at the AMC Desert Star in Baraboo. Not rated, 1:37, three stars out of four.

A few years back, I went up to Door County to write a story on the filming of a movie there, “Feed the Fish.” Although Green Bay native Tony Shalhoub was the big name on the film, the stars were two affable actors I had never heard of before, Katie Aselton and Ross Partridge. They seemed like nice, affable people, suited to a fun lightweight romantic comedy.

But Aselton went on to write and direct the dark thriller “Black Rock,” while Partridge has now written, directed and stars in the beautiful and unsettling new drama “Lamb.” Don’t judge a book by its affable cover, I guess.

Partridge plays David Lamb, a middle-aged Chicago businessman in the grips of a personal crisis, including a failing marriage, trouble at work, and, as we learn later, a personal loss. He’s slouched against his car in a strip mall parking lot when a brash 11-year-old girl, Tommie (Oona Laurence) tries to bum a cigarette off him to impress her friends. As a joke, Lamb suggests that he pretend to kidnap Tommie to freak out her friends. She agrees and hops in his car.

And then the next day, they do it again. Only this time Lamb drives away with her.

“You have to understand that to other people, this looks like a kidnapping,” Lamb tells Tommie. Well, isn’t it? Much of “Lamb” makes us question what’s going on here and exactly how worried we should be for Tommie in the hands of this strange but kindly-seeming man. Both are escaping drab home lives (a quick scene with Tommie’s neglectful parents, played by Scoot McNairy and Lindsey Pulsipher, is almost suffocating in its dreariness), and Lamb insists that his feelings toward Tommie aren’t sexual.

But they are certainly inappropriate for a 47-year-old man to have to an 11-year-old girl. Lamb takes Tommie on a road trip up to Wyoming, attempting to show her the beauty of the world (the widescreen cinematography is breathtaking), so it seems like he’s stretching for some kind of mentor role. But his rationalizations about his behavior, to Tommie and himself, show that a part of him worries that he’s scarring Tommie rather than saving her.

Partridge effectively uses his friendly demeanor to keep us off-balance about Lamb, keep us guessing about whether he has this girl’s best interests at heart. He finds a terrific duet partner in young Laurence, who expertly navigates the shifting layers of wisdom and innocence within Tommie. It’s easy to care about what happens to her, but the film’s more difficult trick is to make us care for Lamb even as we recoil at how he near he gets to a moral precipice. The friendship between the two characters may be wildly inappropriate, but that doesn’t mean it doesn’t have value to them.

In another unlikely Wisconsin connection, “Lamb” was produced by Meg Eslyn, who lived in Madison for several years and shot videos for bands like Screaming Cyn Cyn and the Pons. Unfortunately, the film is only playing in Baraboo for now, but if you’re looking for something a little different at the movies, it’s worth the drive.