Mysterious man (The Lazarus Experiment)
From Tardis Wiki, the free Doctor Who reference
The Mysterious Man was an agent of Harold Saxon that overwatched Saxon's good friend, Richard Lazarus's experiment to make himself younger. He also told Francine Jones that her daughter, Martha (who was The Doctor's companion), that she should not trust the Doctor. This led her to the conclusion of helping Saxon track down the Doctor.
(DW: The Lazarus Experiment)
