The Master commandeers the Doctor's TARDIS, leaving the stranded Time Lord time to work out the mystery of the alien sanctum he's been trying to enter. Inside lies an immense power - the entire Xeraphin race, thought long lost but distilled into a single living essence, ready for rebirth but now suffering a dual gestalt personality, good versus bad, thanks to the Master's meddling with it. As the two Xeraphin halves enter into a struggle for dominance of the whole, the Doctor works for a favorable outcome before the Master can succeed at turning them into his new power source.
Did You Know?
The script for this episode was drastically short, so Eric Saward
asked Peter Grimwade
to contribute a further seven minutes. Grimwade provided various new and extended scenes, including more material involving Bilton and Stapley spying on the Master and later trying to pilot the TARDIS, and additional exposition about the Xeraphin. See more
By the way, if the Master turns up again, don't be surprised. It may take him a little time to discover I left the, uh, Coordinate Override switched in.