Twas the Episode Before Christmas

A man named Joseph is murdered by criminals he testified against and his wife, Mary, leaves her baby in Agnes' apartment. She enlists Maddie and David to help find the baby, and encounters "the three kings" (three FBI agents all called King). The baby's mother eventually turns up at Blue Moon, but Agnes and the baby are gone, and are eventually found at Maddie's house being held at gunpoint. The episode ends with the cast, crew, and their families singing a Christmas carol to the viewers.