Tara and David, time-traveller twins, have been sent on a quest - to save Planet Earth. Living in the Wye Valley in the 21st century, they visit an archaeological dig site, where they discover a mysterious bronze mirror. It transports them, their reluctant cousin Simone, and their puppy Bethan, to the wild Welsh Marches of the fourteenth century. Here, they meet Carys and Hugh, whose family desperately need help...