On Secret Service: The Secret House

Published in Hearst's Magazine, Oct 1915. Collected as chapters 12-13 in the book The Door of Dread
After a pleasant evening meal together in a restaurant, Sadie and her colleague Wilsnach are separated when the latter is called to a phone and the former is soon tricked into getting into a cab. Finding herself captive in a secret house, answering questions by Spymaster Keudell.