A reluctant Solomon (Colin Baker), along with his former associates Egan (David Troughton) and Saul (John Wadmore), have (they think!) escaped Earth and returned to their own dimension. But a mysterious force returns them to Earth and drops them right into the middle of a top-secret experiment involving a young girl's mind powers. They soon find that the experiment has gone wrong and unleashed something deadly...and unless they can find a way to stop it, they and the experiment's team members will all soon be dead!