Usually, when one reads a thriller about a British detective hot on the heels of a group of terrorists and assassins, one would expect to be rooting for the detective.

In the case chronicled in Jo Walton's alternative world science fiction novel Ha‘penny though, the detective, Inspector Carmichael, is pursuing a terrorist cell that hopes to kill Hitler and a quisling prime minister, Mark Normanby, in a desperate attempt to halt Britain's slide into fascism.

The detective in question is gay, a fact that his superiors use to blackmail him into complying with their wishes. And he's a decent sort who despises the regime he works for and looks for a way to quietly leave Scotland Yard so that he can find a job that doesn't wound his conscience.

Even as I rooted for the terrorist gang to succeed and kill Hitler—Walton pulls no punches in her depiction of the horror of Hitler's regime—I could not help also pulling for the detective and admiring his professionalism.

It's an odd sort of thriller that has you hoping the hero will fail, but Walton, while always putting herself on the side of freedom, brilliantly exploits this sort of ambiguity over and over again. One of the plotters, indispensable to the success of the plot, is a despicable Stalinist, horrible and hypocritical in the way she treats other people. The reader comes to admire another character who is an IRA bomber and assassin. Hitler, although obviously a monster, turns out to be likeable when he makes small talk with one of the narrators at a party.

Walton uses this sense of irony to make arguments for freedom that would sound stale and hackneyed if expressed in an ordinary way.

For example, in Chapter 18, Carmichael's assistant, Royston, reports that another batch of Communists have been rounded up.

“I hear they arrested another lot of them yesterday, ones who'd come around protesting about their paper being closed down,” Royston said.

“That's not a crime, surely?” Carmichael asked mildly.

Royston laughed.

The absurdity of closing a newspaper few people likely read in a regime seeking to preserve the illusion of freedom is thus coupled with the amusing irony of Communists' putting themselves at risk on behalf of free speech.

The story is told in a series of alternating chapters, with chapters narrated by Viola Larkin, an actress, alternated with chapters narrated by Carmichael.

Larkin comes from a family of famous sisters, the Larkins (obviously modeled on the Mitford sisters). Very much against her wishes, she is recruited into a plot to kill Hitler and the quisling local leader, Normanby, with a bomb during the premiere of Hamlet. (The genders in the performance have been reversed; Larkin is supposed to help coordinate the attack while performing the lead role).

The reader roots for the plot to succeed, of course —Walton unsparingly describes the massacres and tyranny of Hitler's regime—but because of Walton's skill, one also finds one's self eagerly watching Carmichael pursue the conspiracy.

Walton, a native of Wales who now resides in Canada, varies her settings from one project to the next, but has often displayed her love on history. In the preface, she notes that two of the incidents presented in her book did in fact really take place—the Irish Republican Army really did conduct a bombing campaign against England in 1939, and the Luftwaffe did accidentally drop a bomb on Dublin during its bombing campaign against the English.

Ha‘penny is a sequel to the author's Farthing, which I plan to read soon. The final book in the trilogy, Half a Crown, will be published in September 2008 by Tor.