The Doctor's plans against the Krotons are coming to fruition. But will he be betrayed by the ambitious Eelek?
Eelek takes over the Gonds and is determined to launch an attack on the Krotons. Meanwhile, the Doctor and Zoe try to discover the creatures' weaknessâ€¦
The Doctor and Zoe's investigations cause the Krotons to summon them into their ship. A tremendous danger lurks withinâ€¦
For centuries the alien Krotons have hidden inside their Machine in the Hall of Learning, educating a small settlement of Gonds and selecting the two best students of each graduating class to become their Companions. This is seen as a great honour until the Doctor and his friends arrive and discover the terrible truthâ€¦moreless