"RALPH CONTINUES to keep Hunter alive," says a printmaker, speaking of the British cartoonist Ralph Steadman and his American collaborator, journalist Hunter S. Thompson. "And, in a way," the printmaker continues, "Hunter keeps Ralph alive."

But while Ralph remains alive, Hunter, of course, is very much dead: He blew his brains out in 2005. Nonetheless, Thompson's spirit looms over For No Good Reason, a documentary about Steadman that sometimes wishes its subject was Thompson. But Steadman, too, is a wholly worthwhile star: The most enthralling passage in For No Good Reason tracks the artist's creation of a new work. He flings black ink, searching for inspiration in chaos. He zeroes in, then begins layering so quickly and seemingly without regard as to make the entire process appear impossibly easy.

For Thompson freaks, however, there's little left to exhume: Nearly all of this film's footage and tales of Thompson can be found elsewhere and in greater detail. Meanwhile, Johnny Depp appears here as both a narrator and participant—despite the fact that aside from commercial considerations, he's useless as both a witness to and an explainer of art. But if Depp's presence was required to get this film made—and if it points even a single virgin eyeball toward Steadman's cackling, psychedelic political visions—it's a price well worth paying.