What is an example of irony in the novel, Arch of Triumph?

Haake, the Nazi Gestapo interrogator who brutalized Ravic and Sybil, and was the cause of Sybil's suicide appears periodically in Paris on secret missions. Once Ravic recognizes him, he begins plotting his revenge. After murdering Haake, Ravic feels purged, especially of his painful memories of Sybil: "Haake's death had freed Sybil's face from its look of death ... At last he could have peace." Yet, in an ironic twist, Ravic's revenge and peace occur on the day before World War II begins, and the next day he is sent to a French internment camp.