Rankin Gorlay and his wife Carol are a middle-class family who practice wife-swapping with the Harts, a working-class family from the local estate. When the Harts take a long awaited holiday, they leave their delinquent son Marcel with the Gorlays for a week. But everywhere Rankin and Carol take Marcel, death and destruction follow in their wake. Gradually they realise that it isn't all coincidence, and that somehow Marcel is causing these deaths. Rankin and Carol are not too surprised to find a human skull in Marcel's suitcase and a cabalistic circle chalked on the floor. But just how much power does he hold over them?