The TARDIS is diverted to England in 1572, and the Sixth Doctor and Peri meet John Dee — "mathematician, astrologer, alchemist, magician, and the greatest mind of our time". ("Only of your time?", the Doctor asks, unimpressed.) But what brought them here? When the Doctor discovers that Dee and his assistant have come across a "great disturbance in the cosmos, in the constellation of Cassiopeia", he realises that they are all in terrible danger.
According to one account, the Master had the appearance of Roger Delgado while on Gallifrey. According to another, he had Anthony Ainley's likeness. According to another one, the one with James Dreyfus's appearance was the incarnation who ran away from Gallifrey.
While fighting to extend his life at the end of his regeneration cycle, many bodies were possessed by the Beevers incarnation, but all kept somehow reverting to his real being until he finally regenerated into the MacQueen one. Hence, these sections cannot be strictly chronological
