"You know me then?" asked the Eighth Doctor, a little tentatively.

"You're the Doctor," replied Fitz, a slight frown worming its way on to his forehead.

"Yes, yes, yes, the Doctor, of course I am." The Doctor smiled, genuinely pleased to see a familiar face, even if for the moment he couldn't quite put a name to it. "But, er, Doctor who?" he added, hopefully.

The Doctor and Fitz are back together at last, but the Doctor is not the man he once was — which is a shame, because Fitz has promised Anji Kapoor that his old friend is Anji's best hope of finding her alien-abducted boyfriend, Dave.

Soon the Doctor, Fitz and Anji find themselves involved in a desperate contest between Pierre-Yves Dudoin and Arthur Tyler the Third, each determined to be the first privately funded man in space. But not all the parties are playing fairly: members of an alien race called the Kulan are helping the Frenchman — and at the far reaches of the Solar System their battle fleet awaits...

Can the Doctor find Dave before the alien contact proves fatal? Who are the secret agents keeping tabs on the rival Space Race teams? Will the Doctor's mysterious blue box finally reveal its purpose? And does the Doctor, now truly a man without a past, have what it takes to stop the Kulan Invasion of Earth...?