It was a few hours before the premiere of Marvel’s “Avengers: Infinity War” late last month, and Benedict Cumberbatch was not about to violate the studio’s ban on spoilers surrounding the penultimate chapter of the most lucrative movie franchise ever.

“Don’t ask,” he said, in response to a mock-question about his turn as Doctor Strange. “All I can give you is a nice recipe for Aperol spritz.”

But Mr. Cumberbatch was happy to speak volubly about another complex work of serial narrative hitting the screen this spring — one that also unfolded over many years, commands an ardent fan base and features him as an unusually intelligent man battling dark forces (albeit armed with vicious wit and bulletproof irony rather than magical orbs).

“Patrick Melrose,” a five-part limited series that debuts on Showtime on May 12, is based on five autobiographical novels by the British writer Edward St. Aubyn, whose exquisite prose and subtle portraiture have won them almost cultish devotion. Published between 1992 and 2011, they follow an upper-class Englishman on a 40-year journey of recovery from horrific childhood abuse, addiction and the soul-killing snobbery of his milieu.