The Spy Double

Published in Argosy, August 15, 1936.
This is not a Fox Elton adventure but it is set in the same universe. The operative in this mission, Captain Morton Steele, also works for Colonel Rand, just as Elton does.
"Intrigue and death ride hand in hand over spy-infested war-time Holland." Morton Steele is determined to bring down a highly effective spy cell run by the German spymaster von Gorst who has been operating in the Netherlands for far too long.