Mariechen Pagenkoff, known as Mrs Molly Kirby, was a native of Coblenz, but had been educated in England, and had lived here the greater part of her life until she had lost all trace of her foreign birth. Her husband had been a German shipping-agent in Glasgow, and at the same time a secret agent of the Koeniger-gratzerstrasse. But he had died two years before, leaving her a widow. Her profession of spy had brought her into contact with Lewin Rodwell, and ever since the outbreak of war the pair had acted in conjunction with each other in collecting and transmitting information through the various secret channels open between London and Berlin, and in carrying out many coups of espionage. Mrs Kirby lived very comfortably--as the widow of a rather wealthy shipping-agent might live--in a pretty flat in Cadogan Gardens, and to those around her she was believed to be, like Lewin Rodwell, most patriotic and charitable. Indeed, she had done much voluntary work for the charitable funds, and had interested herself in the relief of Belgian refugees, and in the work of the Red Cross. "The day after you had been to the office," Rodwell explained, "I went down there upon one or two matters which required attention, and, after a couple of hours, I told Charlesworth that I wanted to glance at a certain ledger to verify a query. The book was brought, and as I carelessly searched through it in Charlesworth's presence, I discovered some documents. We opened them, when, to our great surprise, we found letters in German, there being enclosed in one a ten-pound note." "What did old Charlesworth say?" asked Mrs Kirby, with a smile upon her red lips. "Well, as he can read German, I allowed him to digest the letters. The old man was dumbfounded, and exclaimed: `Why, young Sainsbury kept this book! Look at this letter! It's addressed to "Dear Jack"! Is it possible, do you think, that Sainsbury was a German spy?'" "What did you say?"