"Doctor Who: The Black Guardian Trilogy" - This collection includes "Mawdryn Undead", "Terminus", "Enlightenment" and "Enlightenment: Special Edition". "Mawdryn Undead": The Black Guardian recruits a young man named Turlough to assassinate the Doctor. Although outwardly an ordinary pupil at a boys' private boarding school, Turlough is in fact an alien who believes that the Guardian will return him home if he succeeds. "Terminus": The TARDIS attaches itself to a space liner after Turlough, still under the Black Guardian's influence, damages its controls. The liner docks with what appears to be a hulk floating in space. This is Terminus, which claims to offer a cure for lazar disease. "Enlightenment": The White Guardian warns of impending danger and directs the TARDIS to what appears to be an Edwardian sailing yacht, the SS Shadow, but is actually one of a number of spaceships taking part in a race through the solar system, the prize being Enlightenment.