Basically, Tod Friendly and the narrator are the same person. Friendly is about to die, and his mind creates the narrator, an alter ego of the doctor. The narrator is unaware of the Friendly's past, and so the story is told in reverse in order for the narrator and the reader to understand the story. The narrator is an innocent version of Friendly. He doesn't understand any of the events until the novel takes us to Auschwitz, exposing the doctor's atrocities he committed there. Friendly has changed his name several times in order not to be exposed as a participant in killing Jews at the death camp. Friendly's original name is Unverdorben, which means pure and innocent. The alter-ego narrator takes on the characteristics of the meaning of his name, which is, of course, horribly ironic.