This film was the only film in Bill Bixby's long career that was entirely filmed outside of the United States.
The film cast includes two Oscar winners: Olivia de Havilland and Helen Hayes; and one Oscar nominee: Jonathan Pryce.
Lesley-Anne Down and Olivia de Havilland were both in North and South (1985); however they did not share any scenes together.
The British Rail poster ("Read this. Pay less.") outside Marylebone station as Luke and Miss Fullerton exit shows posthumously-disgraced ex-DJ Jimmy Savile.
In the film, events occur at Wychwood Under Ashe; in Agatha Christie's 1939 novel it's the hyphenated Wychwood-under-Ashe.