In “The Lesson,” an amusingly taut British thriller playing now in American movie theaters, two novels result from the same events at an opulent country estate.

This chamber piece — a debut feature from both the director Alice Troughton, a regular of episodic television, and the comedian turned screenwriter Alex MacKeith — asks, both tacitly and explicitly: Can any creative endeavor be honestly attributed to a single source?

One of the film’s writers, J.M. Sinclair (a ferocious Richard E. Grant) is a consummate literary star, who hasn’t published a novel since his firstborn son’s suicide. The unscrupulous Sinclair, however, is about to write the final chapter in a new novel, “Rose Tree,” while staying true to his favorite aphorism, “Great writers steal.”

The other scribe, Liam Somers (the Irish actor Daryl McCormack), is a young upstart with writing ambitions of his own. Hired as a live-in tutor to Sinclair’s youngest child, Bertie (Stephen McMillan), to help…