If biology is destiny, as Freud controversially claimed, then perhaps the biology of aging illuminates why Leonard Fife, the protagonist of Russell Banks' exuberant new novel, "Foregone," is such an unreliable if captivating narrator. A Canadian documentary filmmaker and advocate for leftist causes across five decades, Fife is struggling through the final days of terminal cancer, hopped up on meds that scramble his memories and trigger fantasies. The novel unfolds, then, as a series of confessions that may or may not be grounded in fact; that tension is just one of the book's many delights.

On April Fools' Day, 2018 (a wink to readers), a crew of Fife's former acolytes film him in a makeshift studio in Montreal, a coda to a legendary career. But Fife — mesmerizing, iconoclastic and, yes, foolish — veers off-script. Again and again he circles back to his early life (or lives) in the United States, before he fled to Canada in 1968, at the height of the Vietnam War. Did he emigrate as a draft dodger, a conscientious objector, or neither? He's desperate to reveal his secrets to his longtime wife, Emma, who lingers uncomfortably in the darkened room.

Emma may or may not be Fife's third spouse. As Malcolm, the director, coaxes Fife to delve into his work on war deserters, governmental coverups, past relationships with Joan Baez and Bob Dylan, Fife detours into the 1950s and 1960s. As a teenager he'd escaped his Boston suburb planning to fight for Castro in Cuba; he made it as far as Florida. Early marriage and fatherhood pushed him toward a more genteel, conventional track in Virginia, where a second wife and her wealthy family financed his dream of becoming a writer. That marriage petered out, as well — or did it?

It's a thrill to watch Banks pull off so many risky formal maneuvers. "Foregone" is a brilliantly cinematic novel; it moves in and out of the past and present like a camera, with montages, dissolves and jump cuts. There are memories embedded with memories, agonized mashups of Fife's betrayals.

"He isn't exactly sure what he's been waiting for, but he knows if it ever actually arrives and clicks into place while he is alone and idle like this, the very existence of the brittle, flimsy structure that he calls his life will be jeopardized," Banks writes. "The truth will overwhelm his lies. His old life will reach forward and throttle the new one."

The novel's title puns on Fife's fate — it's a foregone conclusion that Fife will die imminently — but it also plays with what's gone before. The moral stakes are high as the documentarian prepares to shuffle off this mortal coil. Banks slips in a few Easter eggs from his own biography; it's no coincidence that "Leonard Fife" has the same cadence as the author's name.

Few writers have explored the regrets of aging and the door-knock of mortality with Banks' steely-eyed grace and gorgeous language. "Foregone" is a subtle yet unsparing achievement from a master.

Hamilton Cain contributes fiction and nonfiction reviews to a range of venues, including the Star Tribune, O, the Oprah Magazine, the Washington Post and the Boston Globe. He lives in Brooklyn.

Foregone
By: Russell Banks.
Publisher: Ecco, 320 pages, $28.99.