5.6 213

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.