Harvest of Time
By Alastair Reynolds
The Third Doctor and Jo are embroiled in a pretty strange predicament. It appears that The Master has called for aid from one of his future selves to help get him out of prison. But unknown to The Master it did not work out the way he thought it would. What The Doctor discovers is that something has gone wrong with The Masters timeline and that a future Master is not coming to save him but instead it appears he is being erased from time. The Doctor has to keep reminding The Brigadier, Captain Yates and Sgt Benton about The Master by giving them a paper with his face on it to remind them who he is. But that is not all. The Sild have arrived on Earth and due to The Masters meddling with time used that signal to come to Earth and proceed to invade. To save the Earth The Doctor must go to the future and with another unsettling alliance with The Master must find the source of the Sild and shut it down to save The Master and the Earth.
