Director Ari Aster established himself as a modern auteur with his previous horror projects, the supernatural chiller “Hereditary” and the sunny daymare “Midsommar.” His latest foray into paranoia is “Beau is Afraid,” a surrealist dark-comedy that portrays the world as an inescapable, Freudian purgatory. The film is relentless, challenging audiences to live within the mind of an unreasonably fearful, sexually repressed shut-in, without a moment to establish the allegorical rules of the movie’s narrative world-building — and does so for three long hours.

We first meet Beau (Joaquin Phoenix) as he confides with his therapist (Stephen McKinley Henderson) his deepest fears about confronting his controlling mother while planning a trip to see her on the first anniversary of his fathers’ death. His plans derail when he’s locked out of his impoverished tenement apartment, later ransacked by a circus of dangerous street vagrants, which leads to a random accident with a vehicle after failing to reschedule his flight. The driver Grace and her husband Roger (Amy Ryan and Nathan Lane) help Beau recover in their upper-middle-class home, but their hospitality becomes yet another hurdle preventing him from making his way back to his childhood home.

When dissecting the psychological torment of his characters, Aster is a potent director and a compelling storyteller. But unlike his previous features wherein his protagonists come to terms with their trauma through the machinations of an external horror conceit, Beau’s torment is self-manifested. This narrative shift indulges a sneering satirical pressure against Joaquin’s tragic portrayal that goads the audience to find absurdist comedy in the mounting stresses of his journey. If you can’t lock into this heightened sense of Kafkaesque dark humor, expect to be exhausted by the endless sequences of existential cruelty.

Despite its patience wearing stylistic ambitions, Aster knows how to strike a mood and set a tone visually. The camera work moves us along Beau’s perspective in such a way that we only experience these aggressions as the protagonist would perceive them. Tropes from horror, dark comedy and surrealist animation are employed to disorient us and reference bizarre genre juxtapositions for their own sake.

Phoenix has made a career out of playing off-putting lonely weirdos, and like his award-winning turn as the menacing Joker or the lonely bachelor in “Her,” he internalizes the role and performs with concentrated vulnerability. Even when the film wants to mock Beau’s torture, Phoenix approaches his character with empathy. The second act, prominently featuring Amy Ryan and Nathan Lane, stands as the most satisfying block of the picture, largely because of their skilled comedic timing. Richard Kind, Patti LuPone and Parker Posey highlight their scenes as well in shorter supporting roles.

For everything in the picture that’s executed with precision and artistic curiosity, “Beau is Afraid” is a bleak and mostly tedious experience, and though there’s less bloodshed than his horrors, the outing felt far less humanistic. The themes of anxiety, poverty and psychosexual Oedipal explorations are often overstated or repeated through overwrought, overlong metaphors. There’s almost enough talented filmmaking here to invite niche viewers to decode this slogging trauma dump, but minimal entertainment beyond its showcase of cinematic experimentation.

Grade: C+