A new Victorian mystery featuring the popular Detective Best. London is in the grip of Irish fever after bombs explode in Whitehall and on the underground railway. Best is sent to Paris where these Irish Americans are plotting their next 'outrage', and obtaining arms for an uprising. En route, he encounters a charming Southern gentleman who informs him that he is helping the French save their vines from a devastating plague. But is this American who he claims to be? And what had happened in the blood-soaked railway compartment found later on the Continental Express? Meanwhile, with Scotland Yard detectives under so much pressure, Best finds it hard to spare the time to investigate the fate of a wealthy young man who may have been lured by a heartrending advertisement in the agony column of a daily newspaper.