Just before Christmas, Freddie and Elsie are chosen by their school to go on a Mystery Bus Trip in their school bus. But the bus and its driver turn out to be very special indeed, and the children are taken to some amazing places, travelling forwards and back in time, and having some exciting and hair-raising adventures. The trip ends with a special Christmassy surprise, but they must try and outwit someone who will try and spoil Christmas for everyone