After six years of soldiering in occupied Austria, Major Angus McCann spends his second day back in London hunting for a quiet pub in which to sip a few beers. But on his third day out of the army, he is called into the ongoing investigation of a crime wave when an Inspector Hazlerigg of Scotland Yard questions him about a young man nicknamed "Gunner" from his military command. A few days after this conversation McCann begins his own investigation into the rash of criminal activity in London. And although inexperienced at his task, he has the good luck of a man who doesn't know in what sort of danger he has placed himself.