Ten years have passed since Muriel Axon was locked away for society's protection, but psychiatric confinement has only increased her malice and ingenuity. At last free, she sets into motion an intricate plan to exact revenge on those who had her put away. Her former social worker, Isabel, and her old neighbors have moved on, but Muriel, with her talent for disguise, will infiltrate their homes and manipulate their lives, until all her enemies are brought together for a gruesome finale.