This is the third and final appearance Sue Randall makes in the series, the other two appearances occurring in Nightmare at Northoak (1963) and When the Bough Breaks (1964).
This is the first of three appearances Ned Glass makes in the series, each time playing a different character. The other two appearances occur in The Chinese Sunset (1966) and Second Sight (1966).
This is the fourth and final appearance Val Avery makes in the series, each time playing a different character. The other three appearances occur in Moon Child (1965), The Chinese Sunset (1966), and Run the Man Down (1967).
This is the second of three appearances Harold Gould makes in the series, each time playing a different character. The other two appearances occur in Man in a Chariot (1964) and Concrete Evidence (1967).
This is the fourth of five appearances Bing Russell makes in the series, each time playing a character involved in law enforcement.