After Martha Jones parts company with the Doctor, his TARDIS collides with another, and he comes face to face with one of his previous incarnations.
The Doctor struggles to help the only remaining crewmember of a crashing gunship. The people of the planet below offer to save his life, but at a dear cost to the life he's lived for hundreds of years.
With the 50th anniversary of Doctor Who about to film, the "classic" Doctors Peter Davison, Colin Baker and Sylvester McCoy are keen to be involved. But do they manage it?
