In the year 2130, Dominick Hide is a 'Corro': a correlator of information. It is his job to travel to the 'flipside' - the time era before the 1999 holocaust - and report on 20th century London traffic to his superior, Caleb. Although Dominick is happy with his partner, Ava, he begins to feel an urge to experience what life used to be like.

Dominick's great aunt Mavis informs him that his great grandfather, also named Dominick Hide, lived in the time period Dominick is studying, in a region called 'Port Beal', and he becomes determined to find his ancestor. With the help of technician Alaric he secretly lands in 1980 and, though initially confused by the habits of 20th century Londoners, he establishes that the area he wants is Portobello Road. He meets clothes-shop owner Jane who, intrigued and attracted by the stranger's other-worldliness, agrees to help him locate his 'cousin', Dominick Hide. Quizzed by Jane's friends in the pub on his origins, Dominick improvises the name 'Gilbey' from a brand of gin.

During Dominick's third visit he and Jane make love, spending the weekend together in Herne Bay. Upon his return to the future Dominick persuades an initially reluctant Ava that there is a more passionate alternative to their sanitised love-making. Meanwhile, Alaric refuses to assist Dominick with any further landings.

Three months later, Dominick again steals away to the past to explain his actions - only to discover that a resentful and disbelieving Jane is pregnant with their child. Realising he cannot conceal this interference in the timeline, Dominick confesses all to Caleb, who reveals that he has been aware of Dominick's actions all along. Dominick is a rare example of a 'genetic time-slip'; it was necessary to engineer his relationship with Jane in order for Dominick to become his own great-great-grandfather. Dominick asks permission to see Jane one last time, but Caleb refuses - officially. He does, however, make the observation that Dominick hasn't seemed too worried about seeking permission until now...

Dominick and Jane - who now believes his story - spend one last day together, Dominick providing for her and their son by revealing the following week's pools results.

In 1988, Jane plays with the seven-year-old Dominick Hide at Herne Bay in 1988, while in 2130 Dominick and Ava visit the same spot with their own baby.