Crabwalk challenges contemporary notions of German national history by showing how events from their Nazi past can be repurposed or reenacted to form a kind of counter-narrative or alternate history. Grass's novel shows that these counter-narratives are not merely word games but can have real effects on people.

The story begins with the protagonist Paul Pokriefke investigating the history of a Nazi ship sunk by the Soviets. The event has personal significance for Pokriefke; his mother had been on board while pregnant with him, and she gave birth in a life boat. The ship was named for a Nazi martyr, Wilhelm Gustloff, who had been murdered by a Jew. Pokriefke finds that this event has taken on a life of its own online, where two people who have adopted the personas of Gustloff and his killer have extensive debates. These debates take on added significance when Pokriefke finds out that his son is in fact the person impersonating Gustloff online.

The question becomes one of truth? Was the sinking of a ship filled with innocent parties a war crime or simply war-time retribution? When Pokriefke's son meets his online opponent, he kills him in a fit of rage when the man spits on the site of a Nazi-era statue of Gustloff. The two men had been friends in real life; it is as if their made-up, online narrative has superseded actual history. In this alternate history, Gustloff kills the Jew, not the other way around. When asked by the police why he did it, the son simply says "because I am German."

Grass suggests that German nationality itself is based on particular historical realities; the Nazi past is left unexamined precisely because coming to terms with it might rupture historical narratives.