Full Episode Summary
Enemy: Professor Lazarus
Back in modern-day London, Martha returns to her family, one day after having left them. Tish, Martha's sister, works for a Professor Lazarus, who claims he "...will change what it means to be human". The family, plus the Doctor, visit his presentation, in which he uses a manipulator to become younger. But soon, defects appear, and younger isn't the only thing he's becoming...