Luther was the commanding officer of a group of German Nazis that attacked Pax Lucis.
The Nazis had captured a lightwanderer and were using it to place a barrier around Pax Lucis that kept out light and warmth. They planned to use the lightwanderer to destroy all of England.
Luther's men captured the Seventh Doctor, and Luther interrogated him. Luther was intrigued by some of what the Doctor told him. However, Luther's men, Herz and Franz, saw it as a sign of weakness that Luther didn't kill the Doctor outright. Herz relieved Luther of command, and Franz shot Luther. When Melanie Bush and Oliver provided a distraction, Luther fell onto the machine imprisoning the lightwanderer, setting it free. Doing so killed him. (PROSE: Special Weapons)