A Silent Panic is a half-hour episode of the television series The DuPont Show with June Allyson. It stars Harpo Marx in a dramatic role, his first. The story takes place during the Christmas season.
from the IMDb: "A deaf-mute witnesses a murder but is unable to tell the police what he knows. Meanwhile the killer and his accomplice seek to find the deaf-mute in order to eliminate him."
You can see it at this link or below: