"House Guest" begins with Sally Mitchell (Peggy McCay) relaxing on a California beach with her son Tony (Billy Mumy), who starts to drown off shore until he is rescued by a stranger, Ray Roscoe (Robert Sterling). Tony's father John (Macdonald Carey) is so grateful to Ray that he allows the drifter to stay with the family for a few days, which extends to weeks. Ray is soon revealed to be rather shiftless, spotted by young Tony flirting with the maid (Linda Rand), then getting involved in an auto accident with George Sherston (Karl Swenson), and later accused of assaulting George's wife Eve (Adele Mara). A blackmailing Ray refuses to leave unless John gives him 20,000 dollars, which John refuses, but when George shows up with a gun to kill Ray, John knocks Ray out in a brief scuffle. George insists on keeping the incident quiet as he fears losing his government job, offering to drive Ray to the hospital alone, later phoning John with the news that Ray has died. Still acting alone, George ends up burying the corpse himself, while John and Sally discover a letter addressed to Ray among their mail, indicating that someone else knew that the deceased was a guest in their home. Also among the fine cast is 72 year old Hollywood veteran Robert Armstrong ("King Kong"), who would retire from acting in 1964, and passed away in 1973.