Stories are nested within stories to steadily diminishing returns in “Company,” a perversely ponderous exercise in hide-the-genre that takes more than an hour to reveal what its game really is. Gathering little tension ahead of a ludicrous twist — one that puts proceedings in a new light while adding no great urgency to them — Casey Affleck’s second feature as writer-director feels altogether less assured than his 2019 debut, the somberly effective post-apocalyptic drama “Light of My Life.” This time staying behind the camera entirely, and handing a demanding lead role to his teenage son Atticus, Affleck again brings an earnest seriousness of purpose to this staggered tale of a mysterious stranger drifting into a household and holding it eerily rapt, repeated across three different eras. But for all the echoey narrative tripling here, the payoff is distinctly muted.

“Company” presents a significant challenge to the marketing teams of any distributors taking it on after its Venice competition premiere — though given the dull peculiarity of the film, coupled with a muted festival reception, said distributors are by no means a given. How does one pitch to audiences a film where its grabbiest story hook is also its most carefully guarded secret? Minus the surprise factor that certainly caught Venice journalists off guard, viewers going in with some idea of what’s coming will be even more perplexed by the coy obfuscation and molasses pacing of the film’s first two-thirds, which mostly present as the kind of melancholically revisionist period Western one might expect from the star of “The Assassination of Jesse James by the Coward Robert Ford” and “The World to Come.” (And indeed his co-scripter Ron Hansen, writer of the former film’s source novel and the latter film’s screenplay.)