This episode has an unusually lengthy setup; none of the regular cast members put in an appearance until about the 15-minute mark.
Meg Wyllie, who played Great Aunt Ninevah was only 46 years old; the same age as Raymond Burr.
In the complete series DVD collection, the cast list in the end credits is for the season 8 episode The Case of the Sad Sicilian (1965).
When Wayne Jamison and Ernest Stone are playing a game and the phone rings (shortly after 29:00), it is not at all certain what game they are playing. It looks like backgammon, but the board is turned the wrong way and there seem to be three columns on which the pieces sit. It is played with dice, because Wayne throws dice from a dicebox and then advances a piece in a manner that suggests it hops back and forth from one column to another. The only board game that might be similar to this is "Can't Stop" but it wasn't invented until 1980, and it doesn't look the same.