Dominick Hide, a time traveller from the year 2130, is studying the London transport system of 1980. Time travellers are supposed to be observers, and are strictly forbidden to land their flying saucers. One time traveller who broke this rule accidentally killed a dog, changing history and causing many future people to disappear. Inspired by his Great Aunt Mavis, Dominick decides to find his great great grandfather. He begins to land in 1980, where his strange clothes and speech make him seem an eccentric oddball. His quest brings him into contact with beautiful boutique owner Jane, and they fall in love. As Dominick's visits become more frequent and more prolonged, he increasingly risks his indiscretion being discovered by his boss, Caleb Line, and every moment he spends in the past increases the danger that he will catastrophically change the future

Now a respected teacher of temporal observers, Dominick has not visited the past for several years. He is content with his lot, resigned to the idea that he will never again see Jane, the lover he left in 1980, or their son. Then his boss gives him a new mission: to find out what has become of one of Dominick's students, Pyrus Bonnington, who has gone missing in 1982.