Oberst Keller is a character in Call of Duty: WWII. He is a officer wearing grey uniform in the basement of the garrison. The player assumes control of Camille "Rousseau" Denis and is informed that Karl Fischer is in the basement after asking Oberst Huber or Baumann. The player can ask him is he Fischer or tell him the code phrase "Verlaine". If the player tells him the code phrase, he will ask Rousseau to give him her ID papers and ask her to state her name. If she responds "Hanna Muller" instead of "Gerda Schneider" she will be arrested, resulting in a game-over screen.