Doctor Who: Dooms Day: Extraction Point

It's the Doctor's universe. 24 hours to find them. 24 hours to escape death. The finest time-travelling assassin in the cosmos is running scared. Doom's own death is coming for her in a matter of hours. And the only person in the universe who might just be able to save her is the Doctor - so long as it's the right Doctor. But as Doom searches for aid, the hits keep coming in. Kill a crabby Kraal and his replica world! Assassinate a ghost on Satellite Five! Eliminate a living asteroid! Doom finds her talents - and her patience - stretched to breaking point. But these apparently random jobs are linked in a way Doom could never imagine. And when not one but TWO different Doctors get involved, on the trail of an old enemy, the ensuing fireworks might just end the lives of billions. Can Doom solve the mystery before her allotted hours are up? It's not only a planet she must save from destruction, but herself...