X for Extortion

"There''s no deal unless you tell me who killed Lucretia, Thomas! For the love of God, I have to know-"
"She was shot by an assassin."
"But who was this assassin? Who shot her?" he demanded again angrily, leaning forward over the table.
"I did," I said, after a suitably dramatic pause.
He threw his head back and laughed loudly, his arms crossed on his chest. "You?" he said once he''d regained his breath. "You? Thomas Haupner, the violinist? The would-be army officer from some stupid, derelict relic of the British Empire, a trained assassin?"
After returning from a secret mission in occupied France for His Royal Highness, George, the Duke of Kent, Lieutenant-Colonel Thomas Haupner is looking forward to a cup of tea, a hot bath, and the sleepy head of his American lover, Major Henry Reiter on his shoulder when he wakes up the next morning.
However, along with items Tommy has recovered for the duke, he has also discovered a secret stash of documents, which, when opened, prove to be a poisoned chalice. Tommy and Shorty find themselves caught up in a dangerous web of lies, enemy agents, assassins, and traitors. In an effort to save the reputations of not only their friends, but men and women high in both society and in the government, they themselves become victims of I.K.S., a former World War One international extortion ring, which has risen, phoenix-like, from the ashes of bomb-devastated London.