Lucy Harbin (Joan Crawford) is a woman who goes berserk, when she finds her husband in bed with another woman. With her three-year-old daughter accidentally witnessing the grisly act, Lucy axes the couple to death. She spends twenty years in a mental institution for the double murder.
After she is released, she moves in with her brother, Bill (Leif Erickson), his wife, Emily (Rochelle Hudson) and Carol (Diane Baker), her own daughter who is now twenty-three. Her nightmare is over…or is it? When a spate of axe murders start occurring suddenly in the neighbourhood, police think Lucy has reverted to her old ways. The truth is finally revealed.