Filmmaker Heather Ross combines a variety of striking visuals — including creative nonfiction reenactments, animated comic book panels/collages, archival stills/film clips, vintage stock footage and conventional talking heads — to assemble For Madmen Only: The Stories of Del Close. Described by Bill Murray and others as “the most famous person you’ve never heard of,” Close was the monumentally influential mentor who counted dozens of comic powerhouses among his students. Close was also one of the early practitioners to recognize long-form improvisational performance as an art in and of itself. He died of emphysema on March 4, 1999, just a few days shy of his 65th birthday.

Ross is not the first person to document the Del Close phenomenon, but For Madmen Only covers an impressive amount of historical and spiritual territory in just under an hour and a half without ever suggesting that significant milestones were ignored or excised. Close fanatics might quibble over the real estate afforded one thing or another (the sections devoted to Close, played by James Urbaniak, working on some of the twisted autobiographical material that would end up in the DC comic Wasteland, would be better in slightly smaller doses). But one has to admire the way in which Ross honors her subject by devising something as willing to take risks as the guru himself.

The “who’s who” of talent in interviews new and old undoubtedly presented Ross with a nearly endless supply of tough choices. And despite the late critical aside that Close had a tendency to favor white boys — who are thoroughly represented in the movie — the For Madmen Only lineup also includes key input from Tim Meadows, Amy Poehler, Tina Fey and others. Arguably, the most important on-camera subject to speak with authority on Close is Charna Halpern, the collaborator, partner and ImprovOlympic cofounder who perhaps best understood Close’s unique gifts and harnessed and honed the Harold concept into the version most fully appreciated by audiences.

Given the vault of stories focused on Close’s prodigious appetite for smoking, drinking and drug-taking, Ross elects to maintain a kind of balance between the man’s darkest moments and his most magnificent impulses in the direction of generosity and humanity (evident in Close’s belief that the tools and techniques of improv could be taught to any willing student and not just sublime natural talents like John Belushi and Gilda Radner). Even though Close would come to embrace his role as sage bestower of comedic wisdom in the laboratory setting, For Madmen Only does suggest that he experienced significant frustrations throughout his career.

The first of these professional potholes involves the jaw-dropping tale of Close’s membership in the Compass Players, his romance with Elaine May and the insult of being left out when May and fellow Compass performer Mike Nichols decided to do their own thing after making it to New York. Close’s rocky yet indelible relationship with Chicago and Second City follows, and Ross shows the emerging pattern.

Undoubtedly, For Madmen Only is essential viewing for comedy and improvisation hounds, but Ross must be praised for her ability to appeal to general audiences as well as hardcore scholars. In their valuable 2012 “Studies in American Humor” article on Close, Diana DePasquale and Melinda M. Lewis wrote, “As with any great teacher, it is impossible to quantify Close’s impact with finality, as it continues to permeate culture and entertainment.” Thanks to Ross’ film, Close’s legacy will reach the next generation of performers-to-be.

Greg Carlson (@gcarlson1972) is an associate professor of communication studies and the director of the interdisciplinary film studies minor program at Concordia College in Moorhead, Minnesota. He is also the film editor of the High Plains Reader, where his writing has appeared since 1997.