Mother's boy Lionel Cosgrove is 25 and has never been kissed. Then one fateful day in 1957, Lionel's uneventful existence changes forever. Drawn to the lovely Paquita, a young Spanish girl from the local corner shop, the couple plan a tryst at the nearby zoo. Thinking themselves alone at last, the young lovers are unaware that their every move is being observed from the bushes by Lionel's possessive mum. Sneaking close, mum stumbles against a cage which contains a vicious Sumatran Rat Monkey which duly sinks its toxic fangs deep into her flesh. When the strange wound transforms into a putrefying virus, Lionel and the unwitting Paquita are sent spiralling into an endless nightmare...