Edgar Wallace 
When The Gangs Came To London 

Tough, ruthless gangsters from Chicago descend on London and for two weeks their violent campaign of murder and intimidation holds the city in a crushing grip of fear. Scotland Yard has never seen such an onslaught. When a lull ensues, Captain Jiggs Allermain of the Chicago Detective Bureau suspects the rival gangs of forming an uneasy alliance. Suddenly a shot rings through the House of Commons – unleashing an outburst of terror even more bloody.