When she was 8, Ruth Wilson liked re-enacting movie scenes with her two rambunctious brothers. One of her favorites, she recalled the other day, was the ending of “Platoon,” in which Willem Dafoe, peppered by bullets, collapses in slow motion on a verdant field.

Some time ago, Jimmy Fallon urged Ms. Wilson to replay that sequence for his late-night audience. She was game, kicking off her pumps, stepping to center stage in a sexy little cocktail dress, taking one imaginary bullet after another, and writhing theatrically before sinking to the floor.

There was something feline in her performance. But then, as she would tell you, she was doing what comes naturally. There is no obvious slink in her gait, no purr in her voice, though in an interview she extended a leg elastically to show off her pale Chanel sandals. In Manhattan last week to talk up “The Little Stranger,” the new gothic thriller that opens on Aug. 31, she confessed to feeling a kind of eerie kinship with cats.

“A cat is incredibly physical, and as a performer I’m physical,” she said. “If I feel emotions, they move through my body in a way that is sensual. I’m not necessarily in control of that.”