After a meeting in space with a group of unseen aliens the Doctor (Tome Baker) returns to Gallifrey and claims the presidency of the Time Lords. Leela meanwhile tries to work out why he is behaving out of character. At his induction, the Doctor is 'crowned' with a device giving him access to the Matrix. He then arranges for the transduction barriers around Gallifrey to be put out of action by K9. When this is done, his alien 'friends' materialise. They are telepathic invaders called Vardans...