Something vast is stirring in the dark and with the dark prophecy of the Doctor's song finally ending he arrives on Earth to face an old nemesis. But another threat looms on the horizon. Multi-millionaire tycoon Joshua Naismith and his daughter Abigail who also have their eyes set on the Time Lords deranged enemy. The Immortality Gate awaits the Doctor and an even greater foe from his past awaits to make their presence known. Will it be he who will knock four times? With the help of his old friend Wilfred Mott, grandfather to former companion Donna Noble perhaps he will find out who!