Half this title's premise would be revisited 5 years later, in Sitting Duck/Sweet Suzi Swann (1982), where Mr. Roarke himself becomes the hunted to Chuck Norris' hunter.
In Return to Peyton Place (1961), Eleanor Parker and Carol Lynley played mother and daughter. Here they play sisters.
Exactly 3 years later, Bill Bixby himself would be the hunted, this time in his own series, in The Snare (1979). It is unclear if he got the inspiration from this title here, as it is a famous premise, revisited many times over on television, particularly in the '70s.
At one point, Greenwood picks up a newspaper with the headline "ALLIES REPULSED AT NETTUNO." This fixes the date of his original liaison with Francesca as late January/early February 1944, after the landings at Anzio, Italy.
In the beginning Bill Bixby comments on Mr Roarke's work : "you are a magician" . 4 years before he starred in the series The magician, in which he performed many of the magic tricks himself.