Published in three issues of Adventure, August 1, August 15, and September 1 1930.
As per one review at the time: "The story deals with a brave young American [Fox Elton] who unravels the devious threads of a great Boche plan to storm Paris. The sex interest is supplied by a Spanish vixen and a handsome, undecipherable German girl. The former has sold herself to the Vaterland. Her chief job is to lure innocent American spys (sic) into the tolls of the German intelligence office through her unlimited supply of passion.
The book is full of intriguing and machiavellian scheming. Blood drips off every sentence. Dirty work goes on in dark alleys. All the devices of suspense and terrorism that have been developed since Walpole wrote The Castle of Otronto have been dragged in."