Turlough and the Earthlink Dilemma

Of all the companions ever to travel with the Doctor in the TARDIS, Turlough was the most enigmatic and the most disturbing. Exiled from his home world, he saw the Doctor as a means of escape from Earth - and for that he was prepared to kill.

But just who was Turlough? And what happened to him after he left the Doctor?

Now Turlough has returned to Trion, but to a Trion much changed since his exile. Who are the mysterious Gardsormr? What is their secret purpose? And what is the shocking and terrifying link between Trion and planet Earth?