Gallifrey, planet of the Time Lords. Summoned home by a premonition of murder, the Doctor discovers a dark conspiracy at the highest levels of Time Lord society... and his oldest enemy, who poses a threat to the existence of Gallifrey itself...

The President of the High Council has been killed and the Doctor is the prime suspect. The Time Lords are eager to dispense quick justice and the Doctor must race agains the clock to discover the truth... and an old enemy.

The Doctor has entered the computation Matrix to prove his innocence. But his opponent is prepared for him and the two engage in a mental duel to the death.

The Doctor has won his fight in the Matrix and revealed the assassin. But the Master is not defeated and sets a plan in motion that could destroy the Time Lords.