In present-day London, an elderly man named Professor Richard Lazarus announces on television that he will demonstrate a device that will change what it means to be human. Intrigued by this statement, the Tenth Doctor joins Martha to go to the launch party at Lazarus Laboratories, where they meet up with Martha's sister Tish, who works there. Lazarus steps inside a capsule, and emerges as a much younger man. Using a sample of Lazarus' DNA, the Doctor and Martha find that Lazarus had successfully managed to instruct his genes to rejuvenate with sound waves, but also activated something in his DNA, which is trying to change him into something else.