Don Argott and Demian Fenton's Last Days Here is a rock documentary by the Philadelphia filmmakers who created the Barnes Foundation argument-starter, The Art of the Steal. Their new film focuses on Bobby Liebling, leader of the 1970s doom-metal cult band Pentagram.

It starts with scenes shot in 2007, when the now 58-year-old Liebling is a crack-addicted, frizzy-haired waste product living in the "sub-basement" of his parents' suburban Maryland home.

We meet Liebling with Sean Pelletier, a decades younger superfan. Pelletier sees the early 1970s recordings of Pentagram, which one metal maven describes as "a street Black Sabbath" in the movie, as the work of a visionary who "speaks truth that not many people see or know."

After discovering Pentagram's obscure but abundant oeuvre on old vinyl LPs, the mutton-chopped Pelletier - nicknamed "Pellet" - finds Liebling. He befriends him and becomes his manager, dedicating himself to cleaning up the also heroin-addicted rocker, and getting him back to making music.

It's a dirty job, but one that Pelletier is, at least at first, happy to take on.

"I was obsessed with this band," Pelletier says. For him, working with Liebling "is like being a devout Christian and walking down the street and bumping into Jesus."

Last Days Here bears obvious similarities to the delightfully entertaining 2008 documentary Anvil! The Story of Anvil, about the titular star-crossed Canadian metal band. But Argott and Fenton's movie, which was a hit at the South by Southwest Film Festival last year, carries more weight.

That's partly because Pentagram's music, not that much of which is heard in the movie, is dank, difficult stuff.

But it's mostly because the bug-eyed Liebling is a dangerous character who looks like Marty Feldman crossed with Beelzebub. Often feeble and sometimes feral, he's done so much destruction to himself and to every relationship he's ever had, that you watch with little hope he'll make it through the movie alive, let alone get back up on stage.

Asked if he's ever done anything besides play rock-and-roll, he has a straightforward answer: "Drugs."

His relationship with his parents is particularly heartrending. Liebling's father, a former foreign-policy adviser to Presidents Johnson, Nixon, and Ford, estimates they've spent $1 million supporting their son.

And while his parents realize they're seen as enablers for their crack-addicted adult son, they can't imagine not serving him his favorite Fig Newton cookies when he asks, let alone kicking him out of the house and risking that he die on the streets.

Just when the movie seems unrelentingly grim, however, things take an unlikely turn for the better. Last Days Here heads north on I-95, and Liebling miraculously meets a much younger woman from Philadelphia who finds his charms irresistible. For a while, anyway.

In its latter stages, the doc becomes not only a bromance, but also a romance, and maybe even a redemption story. "I want to live," Liebling says early on, looking straight into the camera, putting Last Days Here's existential cards on the table.

Argott and Fenton play them effectively throughout, right through to a surprising finish.

Last Days Here ***1/2 (out of four stars)

Directed by Don Argott and Demian Fenton. With Bobby Liebling and Sean Pelletier. Distributed by Sundance Selects.

Running time: 1 hour, 30 mins.

Parent's guide: No MPAA rating (profanity, drug use) 

Playing at: Ritz at the BourseEndText