In a college town two schoolgirls live with their widowed father Luke, a gentle well-educated man, meticulous and orderly. Elvira and Spinny are watchful, however. For Luke plans to remarry - and has chosen Mary, another academic, who threatens to supplant the girls in their father's affections.

But soon the threat to their world is removed - when Mary falls to her death. Hardly an accident, but just who is to blame?