The Dread Men - a Nat Frayne mystery, #4

Detective-Inspector Nat Frayne of the London Metropolitan Police has seen numerous hanging victims, both official and self-staged. But never one so well-dressed, right down to the topper tilted slightly askew by the noose. In fact the victim's flash attire mark him as one of the Swell Mob, London's criminal elite. And the marks of brass knuckles on his face mark this as murder. But who in London dares challenge the Swell Mob?Only one candidate springs to mind.
The newly-arrived Dead Rabbits, a havoc-prone Irish gang from New York City now seeking to expand their brutal form of enterprise to London. If the Dead Rabbits gain a foothold, they can recruit from the thousands of Irish who came to London fleeing the Hunger, and finding only poverty and scorn, remain hungry still. The Rabbits must be stopped. So proclaim the Voices From On High. But as to exactly how, they'd rather not know.
Just the sort of job Scotland Yard reserves for its favorite ask-me-no-questions-and-I'll-tell-you-no-lies detective, Nat Frayne.