Whose portrait does Rachel incorrectly assume once hung in Stefan's home in the novel, The Aftermath?

Rachel incorrectly assumes that the missing painting was a portrait of the Führer (because all Germans had one of these, she says), which Stefan removed to avoid suspicion. He is incredibly insulted when Rachel makes the accusation to his face, since he detested Hitler and his regime, and it turns out that the missing painting was a portrait of his dead wife Claudia.