Waking in an unusual forest with no memory of how he arrived there, the Master has little choice but to seek help from other survivors. But what is it they've all survived?
On the planet Trabus, the Master discovers a society where nobody is innocent and the only true crime is to be a less successful villain than those around you.
At the mercy of an ancient and powerful race, the Master calls upon his oldest friend in his hour of need. The problem is he doesn't recognise this incarnation of the Doctor - while the Doctor knows this Master all too well.