In the conclusion of the four-part story "Mawdryn Undead," the Doctor (Peter Davison) risks giving up his ability to regenerate in order to rescue several innocent victims of the Black Guardian's time-hopping mischief. And what has become of Turlough (Mark Strickson), the baby-faced teenager whom the Guardian has chosen to assassinate the Doctor? Originally telecast on February 9, 1983, "Mawdryn Undead, Episode 4" was written by Peter Grimwade. ~ Hal Erickson, Rovi