starstarstarstar-outline(3 stars)

If Joanna Harcourt-Smith hadn't existed, a screenwriter might have had to invent her.

Harcourt-Smith, who died recently at the age of 74, was a jet-setting denizen of the ’60s and ’70s at their most hedonistic: The daughter of a prosperous family, she effortlessly joined various fabulous entourages in such places as Marbella and Gstaad. At one point in the documentary “My Psychedelic Love Story,” she recounts fetching up in Manhattan in 1972 and crashing with Diane von Furstenberg because, why not? “Those are just the people I grew up with,” she says with French-accented nonchalance.

In other words, Joanna Harcourt-Smith is a marvelous creature, and she provides delightful ballast to “My Psychedelic Love Story,” which centers on her relationship with Harvard psychologist Timothy Leary. By the time she met him, Leary’s outspoken advocacy of LSD had landed him in prison, from which he had escaped to go on the lam. The two met through a mutual friend (who was an international arms dealer, natch), and felt an instant connection they attributed to destiny. They immediately dropped acid and seemingly kept tripping throughout sojourns in Switzerland, Beirut, Kabul and, eventually, California.

The fact that Harcourt-Smith was under the influence throughout the first few months of her romance with Leary made her curious, in retrospect, about whether she was manipulated as an unwitting source for federal agents investigating the controversial Pied Piper. When she saw Errol Morris’s engrossing documentary series “Wormwood,” about the CIA’s covert LSD program, she reached out to the filmmaker to tell him her story and, maybe, get to the bottom of it. Leary eventually turned into a government informant, an event likened to “hippie Watergate,” for which many of Leary’s misogynistic friends blamed Harcourt-Smith. (Allen Ginsberg’s accusations were particularly repugnant.) As “My Psychedelic Love Story” opens, it’s clear that she’s still uncertain herself how it all went down.

Morris’s strength has always been to allow his subjects simply to speak (his editorializing can be less effective, as the recent film “American Dharma” demonstrated). Here, he trains his camera on the still-beautiful Harcourt-Smith in her attractive wood-paneled home in Boston and allows her to emerge as an exceptionally charming, self-aware and astute narrator — if not always an entirely reliable one.

“My Psychedelic Love Story” is essentially an illustrated monologue, with Morris editing together quick montages of period photographs, tarot cards, op-art titles and neon-colored graphics to provide visual interest, often with LSD blotters used as witty backdrops and recurring motifs. The result is an absorbing yarn and yet another lens on that era’s social history that baby boomers are now excavating with frantic enthusiasm before their sources transition to another astral plane. Luckily, Morris caught up with Harcourt-Smith before she left for the next stop: She’s the best thing about “My Psychedelic Love Story,” and a far more sympathetic and compelling character than the man she almost risked her life for.

TV-14. Available Nov. 29 on Showtime. Contains mature thematic material and brief nudity. 101 minutes.