"It doesn't take the creation of a whole new universe just to kill a cat."

With Fitz gone to his certain death and Anji back at work in the City, the Doctor is once more alone. But he has a lot to keep him occupied.

At the Naryshkin Institute in Siberia, scientists are busily at work in a haunted castle. Over a century earlier, creatures from a prehistory that never happened attack a geological expedition. Pages from the lost expedition's journal are put on display at the British Museum, and a US spy plane suffers a mysterious fate. Deep under the snowy landscape of Siberia the key to it all remains trapped in the ice.

Only the Doctor can see that these events are all related. But he isn't the only person involved. Why is Colonel Hartford so interested in the Institute? Who is the mysterious millionaire who is after the journal? How is the Grand Duchess, descendant of the last Tsar, involved?

Soon the Doctor is caught up in a plot that reaches back to the creation of the Universe. And beyond...

...to Time Zero.