After suffering a nervous breakdown, a woman moves into a new house with her husband. She soon begins to suspect that her husband and his sister are up to no good and may have had something to do with her breakdown.

Greg Sanderson is helping his wife, Jan, to recover from a nervous breakdown and revive their strained marriage. Their privacy is interrupted by the arrival of Greg's stunning and mysterious sister, Laura. Jan's paranoia deepens as she suspects that Greg's and her sister's relationship is too close. In her desperation, she confides her fears to the landlord but his weird reaction only creates more confusion.