The lights go down, the Gotham skyline flickers onto the screen, and for a while “Clayface” looks like a familiar kind of tragedy. A street kid with a gift clawing his way toward the big time, a city that chews people up, a crime boss who ruins everything with a single act of violence. James Watkins, directing from a screenplay steeped in the darker corners of the comic-book canon, lets that story breathe before he pulls the floor out from under it. By the time the credits roll, the film has become something stranger and nastier: a horror-thriller about a man who gets exactly what he wished for.

Tom Rhys Harries plays Matt Hagen, and the film opens on his meteoric rise from the alleys of Gotham to the marquee lights of Hollywood. Harries brings an easy, hungry charm to the early scenes, the kind of leading-man confidence that makes his fall feel genuinely brutal. When a local crime boss (Max Minghella, slippery and controlled as John Borrelli) sets in motion the events that leave Hagen horribly disfigured, the actor’s transformation is less a matter of prosthetics than of posture. He shrinks. He hides. Abandoned by his team and with nothing left to lose, Hagen does what desperate men in genre pictures always do, and the film gives him a cutting-edge treatment that miraculously restores him to his former self.

That is where “Clayface” stops being a comeback story. The treatment works - too well, and not only on the surface. Something in Hagen’s grip on reality comes loose, and Watkins, working in science fiction territory with a horror filmmaker’s instincts, tracks the unraveling with unnerving patience. The film’s middle stretch is its most unsettling, as the audience is made to share Hagen’s uncertainty about what is real and what his mind has sculpted for him. It helps enormously that Naomi Ackie is on hand as Caitlyn Corr, grounding the film in something human and steady while everything around her lead character turns to liquid.

The supporting cast is deep and largely British, which lends the Hollywood sections a pleasing friction. Eddie Marsan, David Dencik, and Francesca Corney fill out the margins with lived-in precision, while Ruby Sear as Theresa and Wil Coban as Bones give Hagen’s orbit the texture of people who knew him before the fall and no longer recognize what came back. It is Harries, though, who carries the weight. His performance in the back half is a study in compartmentalized rage, a man convinced he is conducting a symphony of revenge while the music grows increasingly dissonant. “The treatment gave me back everything,” he says at one point, and the line lands like a warning rather than a victory, though the film wisely resists spelling out exactly what he means.

Watkins, whose previous work has shown a facility for sustained dread, keeps the 109-minute runtime lean. There is little fat here, and the film’s genre-blending - horror, thriller, and science fiction in roughly equal measure - feels less like hedging than like three ways of describing the same nightmare. The physical production leans on practical texture and shadow, with the transformation effects used sparingly enough to stay disturbing. By the final act, the revenge narrative has curdled into something more destructive, and the film refuses to tidy it up. “You don’t get to come back from some things,” Caitlyn tells Hagen late in the picture, and the moment hangs there, unanswered.

For audiences who know the character from the comics, there will be plenty to argue about in how freely the film reimagines him. For everyone else, “Clayface” arrives as a chilly, well-crafted warning about the price of reinvention, and about the stories we tell ourselves when the mirror stops cooperating. The TMDb rating of 8.25 suggests early viewers are responding to it, and it is easy to see why: it is a genre film with a face on it, and the face keeps changing. Opening October 21, it asks a question that lingers well after the theater lights come up - when the version of yourself you were given back isn’t the one you wanted, whose fault is the damage that follows?