John Creevey has recently separated from his wife Jennifer and is still obsessed with her and Peter Mullin, the new man in her life. Many years ago his sister Cherry had been murdered and her fiancé, Mark Simms, now John's best friend, had been the prime suspect. When the police reopen the case and Simms is again under suspicion, John begins to doubt his friend's innocence, until Mark tells him of sordid details about Cherry's promiscuous past - and her relationship with Peter Mullin. When John discovers a series of coded messages hidden beneath a railway bridge, he throws himself into solving them, as a way of taking his mind off Jennifer. He believes that he has uncovered the communications of a gang of terrorists, not realising that it is just schoolboys at rival public sc