Oberleutnant Christoph Fischer was one of the commanders of U-boat Eva's Hammer. After B.J. mopped off nearly all Nazis in the U-boat during the event of the New Order, he and the surviving members retreated to the hidden section F of the U-boat to escape the Kreisau Circle and tried to use the radio in radio room in the section to call for help.
After 5 months of hiding, Fischer, like some of his troops, started to lose their mental stability since he and the rest of the surviving Nazi U-boat crews are forced to hide in their own ship. As discontent started growing among his men, he eventually managed to contact the Ausmerzer for help, effectively boasting his moral, and that his days of hiding are coming to an end. However, as insanity takes a whole of him, he welds shut the radio room and tells his men not to come in for the reason of potentially interfering with the signal transmission.
When B.J. comes to destroy the radio system of Section F, he and the rest of the Nazi surviving crews meet their demise, he was killed in the radio room defending the machine that maintained his sanity.