Nadja Regin was replaced by Gianna Maria Canale during production, though one of her poses from a production still of the film is used as a key visual on the British release poster. They just swapped the heads of the actresses.
Originally announced as a co-starring vehicle for husband-and-wife Stewart Granger and Jean Simmons before the female lead was re-cast with Donna Reed.
Final film of Agnes Lauchlan, although she remained active on television until 1978.
In a scene early on at the party, Donna Reed comes into the room where Geoge Sanders is talking to Stewart Granger. She wants to rejoin the party and says, "Do I have to come back with a lasso " This has two references. Firstly, James Stewart speaks to Donna Reed in "It's a Wonderful Life" about lassoing the moon. Secondly, Stewart Granger's real name was James Stewart.