The Quantum Archangel by Craig Hinton

In the fabled city of Atlantis, 5000 years ago, the Priest Kings of Atlantis tried to enslave Kronos, the greatest of the Chonivores, but failed and doomed their magnificent city to a watery grave.

30 years ago The Master attempted the same thing, barely escaping with his life. 2003, in London and the Doctor and his companion Mel have parted company, only to stumble into each other again, while The Doctor tries to stop an old friend from making a terrible mistake, Mel is horrified to learn that her best friend has fallen under the influence of The Master.

As The Master desperately tries to defend himself against the power of Kronos, The Doctor and Mel must overcome their differences. If they don’t, the Quantum Archangel will be triumphant. And if she is, nothing in the Universe will ever be the same again.