Doctor Who: Halflife (Doctor Who (BBC Paperback))

When the TARDIS makes a disastrous landing in the swamps of the planet Sunday, the Doctor has no choice but to abandon Martha and try to find help. But the tranquility of Sunday's swamps is deceptive, and even the TARDIS can't protect Martha forever. The human pioneers of Sunday have their own dangers to face: homeless and alone, they're only just starting to realise that Sunday's wildlife isn't as harmless as it first seems. Why are the native otters behaving so strangely, and what is the creature in the swamps that is so interested in the humans, and the new arrivals? The Doctor and Martha must fight to ensure that human intelligence doesn't become the greatest danger of all.

To lose your memory once may be regarded as a misfortune; to lose it twice looks like carelessness. The Doctor's not himself. He's not quite sure who he is, but he's definitely not himself. It doesn't help that he's forgotten quite why he came to the colony world of Espero in the first place, but he's sure it was something important. Whatever the reason, he's not the planet's only visitor. Before long, he's engaged in the search for a time-bomb - a time-bomb that could have consequences not only for Espero, but for the Doctor himself - and his missing past.