 Peter Milton and Lisa Cleasant are engaged and will soon be getting married. Peter is a brash stockbroker in the City and Lisa is timid and very superstitious. One day they meet Zoe, who is the spitting image of Lisa but very different in personality: she is confident, flirtatious and daring. Being superstitious, Lisa believes that if you meet someone who is your double, you will die within the month. While she is on holiday in Mexico with her equally superstitious mother, Peter and Zoe have a brief but torrid affair. When Lisa returns, she arranges to meet Peter at their "special place" in the woods. But when Zoe also turns up, it looks as if Lisa s superstition might actually happen.