Tunnel Down to Moonrise — Tom Henighan

Jack Toland, a cool seventeen-year-old, is ready for a family holiday in England when his father (a crusading TV scientist) disappears. Jack's father has been spirited away by a group of renegade scientists and thugs who have discovered a means of time-travel, and Jack, his dazzling new friend Cleo, and their mentor Arthur Harker must travel in time back to ancient Stonehenge to try to find him. The young people enter a world of lost mystery and magic, and find a green earth with secrets that may help save our own modern planet from slow destruction.