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.