This is the only episode of the series that is the sequel to another episode.
This is the second show in which a mission arises when Jim and Barney are vacationing together. The other is "Death Squad".
This was Peter Graves' second and final credit as a director.
The house used here belonged to June Allyson & Dick Powell while they were married (1945-1963). This house was later used in the "Hart to Hart" series (1979-1984).
Season six's "Casino", to which this is a sequel, guest starred Jack Cassidy, father of Shaun Cassidy. Ed Gilbert, who plays Armsby here, would go on to play Shaun Cassidy's father in "The Hardy Boys/Nancy Drew Mysteries".