Christina Delasalle, a fragile young wife with a weak heart, and Nicole Horner, a strong, forceful mistress of a sadistic boarding school headmaster plot to kill him. They drown him in the bathtub and dump the body in the school\';;s filthy swimming pool... but when the pool is drained, the body has disappeared - and subsequent reported sightings of the headmaster slowly drive his \';;killers\';; up the wall with almost unbearable suspense...