When Scotland Yard's most celebrated amateur detective is caught photographing the defences of London's most audacious gang of art thieves, he is invited inside - an unexpected courtesy from the charming and brilliant Cloncroskey, who trusts his impregnable fortress over mere secrecy.

What follows is a masterpiece of mutual one-upmanship. Armed with a camera concealing a pistol and an eye for scientific novelty, the melancholy detective deploys the sensation of the age - the newly discovered Röntgen rays - to turn the tables on his host. But Cloncroskey is no ordinary villain. He has weapons of his own hidden in plain sight, behind the canvas of a priceless Old Master.

In this gleefully subversive Victorian comedy, detective and criminal face each other across the barrel of a gun, each too clever to fire - and both too amused to care.