As the film needed to take place during summer, the small town of Murphys, California, was substituted for shooting instead of on location in Connecticut.
In post-production, editing done to the film caused over half of Jerry Goldsmith's music to be left out. The soundtrack was finally available in 1997 along with The Mephisto Waltz (1971).
At the early stages of production, author-producer Tom Tryon wanted Ingrid Bergman for the role of Ada (the Grandmother), and Mark Lester for the dual roles of Niles and Holland. When Bergman passed, on account of a previous stage commitment, Uta Hagen was hired and brought aboard twins Chris Udvarnoky and Martin Udvarnoky.