It is the Tenth Doctor's final journey — but his psychotic nemesis, the Master, has been resurrected on Christmas Eve! Each determined to cheat death, the battle rages from the abandoned wastelands of London to the mysterious Immortality Gate, whilst the alien Ood warn of an even greater danger approaching, as a terrible shadow falls across the entire universe. With the sound of the drums growing louder in the Master's head and an ancient trap closing around the Earth, the Doctor and Wilfred Mott must fight alone. Sacrifices must be made, and the deadly prophecy warns: "He will knock four times."