Four children are evacuated from London during World War II to live with their Grand Parents in the country Side near Bletchley Park where their parents work. Near the house is a lake with an Island and when they explore it they find a cave with four tunnels leading from it. When they go down tunnel one they find they are looking into the future of London's Regent Street, a young girl from 2080 got lost and finds one of the boys and manages to get back with him to 1940. They find tunnel two goes to the past and 3 and 4 have the control machine so they can set the dates to the time they want to travel to, the girl Zara manages to go back to 2080 but finds destruction and devastation all around and realises her parents are dead, so she returns with the four others to live with them.