Franz was part of a group of Nazis, led by Luther, who took over the village of Pax Lucis. They erected a barrier around the village using a captured lightwanderer.
When Herz brought the Seventh Doctor to Luther, Franz looked forward to killing him. He and Herz couldn't understand why Luther refused to kill the Doctor, and conspired to remove Luther from command. Franz then shot Luther.
Franz was killed with the rest of the Nazis by the lightwanderer when it was freed. (PROSE: Special Weapons)