The framed villain
Raven would be the first to admit it; he's no saint. He kills unassuming people for money. His latest target is the minister of Czechoslovakia, and his job is to assassinate him, causing a political instability that will determine the outcome of a war. Ironically, though, his boss frames him, giving him traceable bills from a robbery. He is ironically innocent of this, and his boss is to blame. Instead of killing his target, he decides to kill his patron.
The irony of train drama
This novel belongs to a sub-genre of literature that could be called "Train Thriller," because the whole cast of this story is trapped together on a moving train. This is ironic, because the outcome of this covert drama on a train in the middle of nowhere could have broad implications for world politics. The drama is localized and globalized, all in one narrative. The train is also ironic because all the right people just happen to be on the train at the same time.
Anne's ironic witness
Anne's partnership signifies something deeply ironic. She is betraying her husband, the lead detective, to see things from Raven's point of view, who is literally a paid assassin. Instead of judging him, she ends up sympathizing for him. She makes a change of mind because of the victimhood she faces. Her ironic decisions about Raven can be seen as indications of the depth of her anger and injustice in the face of real victimhood.
The ironic fine
When Raven escapes from the chemical attack on him (they gas him), there is a delightfully ironic moment when he stops Davis on the street and cites him, because he is dressed like an officer. This shows victory because Raven has so much more knowledge than Davis that he can play with him in this way without risking getting caught. The smallness of this victory is ironic too, and the nuance shows Graham Greene's mastery of the craft.
The irony of death
When the plot ends with all the major characters dying together in a Mexican standoff, the irony of their mutually assured destructions signals a deeper irony than the story itself. It can be said this way: Making death the ironic outcome of a human drama is not a free decision; it comes with implications. The ironic implications are that all humans die, and the novel's action is surprisingly irrelevant to the story's ending. The irony makes for a contrast of meaning and meaninglessness.
