“To Dust” runs an hour and a half, and that feels right for a buddy movie whose comedy is as stubborn as this one’s. But the movie is also trying — daring — to seriously consider grief, and that movie could have gone on for much longer. You can feel the script, by Jason Begue and Shawn Snyder, straining to tickle an audience. So it has a bereft widowed Hasidic cantor named Shmuel (Geza Rohrig) team up with Albert, a dumpy, mildly grizzled community college biology professor — and complete stranger — played by Matthew Broderick.

Shmuel wants to know what’s to become of the body of his recently deceased wife. His sorrow mutates into a paralyzing obsession that mystifies, annoys and embarrasses his mother, two young sons and orthodox community. The boys actually think he’s possessed, by a dybbuk in the guise of their mother’s ghost.

This isn’t so much a spiritual or even existential concern for Schmuel as much as a scientific one: What, practically speaking, happens to a corpse? Like, how long does it take to decompose? When his faith and religious leaders have no easy answer, he corners Albert, who reads him one from a forensics textbook.

That should be a wrap, honestly. But the movie has more than an hour to go, meaning we have to tolerate some obnoxious behavior (Albert actually curtails an office-hours session with a needy black student to turn his attention to Shmuel, who as far as I can tell doesn’t pay a dime of tuition). It means forced absurdity. Schmuel arrives at Albert’s, for instance, with a hog whose suffocation, burial and decay are meant to serve as a soothing science experiment. When that doesn’t work, the movie has them hit the road for even more scientific answers.

You can see what this movie is after, something cockeyed but sincere, something in the neighborhood of Paul Mazursky, Elaine May or Alexander Payne. But the writing and filmmaking (Snyder directed) just aren’t quick enough. The film’s heart just isn’t in all of the pig chasing, fence climbing and disinterring. Broderick appears to be here for the comic relief of his mere familiarity, Albert being this diminished echo of his best public-education parts, in “Ferris Bueller’s Day Off” and “Election.”

It’s not until the final minutes when the movie relaxes, the cute (and gross) stuff falls away, and the dark beauty of Shmuel’s suffering finally gets to breathe. Rohrig was the face (and soul) of “Son of Saul,” that formally audacious, morally appalling Auschwitz drama from 2015 (it won the foreign-language Oscar). He never made me laugh here, but he did nearly bring me to tears. Rohrig is so good at searching despair that I don’t know why the filmmakers didn’t just give the whole movie over to him.