"The Lazarus Experiment" is the sixth episode of the third series of the revived British science fiction television series Doctor Who. It was broadcast on BBC One on 5 May 2007 and stars David Tennant as the Tenth Doctor and Martha Jones as his companion, played by Freema Agyeman. On Earth, in present-day London, The Doctor, Martha and her family attend a scientific demonstration by the aged Professor Lazarus. But when the experiment goes wrong, a horrific product of genetic manipulation is unleashed, leaving a trail of death in its mission to live indefinitely.