Robert Preston plays the flip side of his eternally ebullient Professor Harold Hill in Dark at the Top of the Stairs. Preston portrays an early 20th-century harness salesman, fully aware that his product is rapidly becoming obsolete. He tries to compensate for his own lack of self-esteem by cheating on his patient wife Dorothy McGuire; Preston's "other woman" is played by Angela Lansbury. Meanwhile, daughter Shirley Knight falls in love with Jewish boy Lee Kinsolving, who kills himself in the face of relentless bigotry. And McGuire's sister Eve Arden is stuck in a loveless marriage with spineless Frank Overton. Robert Eyer plays the young alter-ego of William Inge, who wrote the Pulitzer Prize-winning play on which this film is based. Eyer's fear of the "dark at the top of the stairs" is meant to be symbolic of the other characters' inner demons, a fact that Inge drives home every three minutes or so. In typical Inge fashion, an unlikely happy ending is reached just before "The End."