"Oh, Mr. Narkom, help me! For God's sake, solve this mystery!" he cried as he gripped Mr. Narkom's outstretched hand in his own and pressed it excitedly. "My father said everything would be all right just as soon as you had the matter in your hands--but it's gone, another! The horror and disgrace of it! I shall kill myself in the end!" "Steady, Captain Digby. Let me introduce you to Lieutenant Deland, who will help you," said Mr. Narkom. The young man acknowledged the introduction dumbly, and his look of appeal went straight to Cleek's heart. "Look here, get a firm grip on yourself, Captain, or you'll be in a bad way," said Cleek. "Here, swallow this capsule. Swallow it, man! There, that's better. Now let me get a clear grasp of the facts of the case, for I know nothing about it whatever. Begin at the beginning, please. Just what _has_ happened? What has 'gone'?" "My latest formula," replied Captain Digby, regaining his composure somewhat. "I am at work on smokeless powder experiments in my laboratory down at my country home in Hampshire. It was specially built for me two years ago when I first took up this work, and I have a special detachment of police and military to guard it." "When did you miss this formula?" "This morning," was the quick answer. "I had been working over it three days--night and day. Last night I tested the stuff, and the results were more satisfactory than hitherto, so I made up my mind to knock off and go to bed--after I had written out the completed formula as usual." "What did you do with it then?" Captain Digby passed a hand, stained with chemicals, over his lined forehead. "That's just it," he almost moaned. "I can't remember. I thought I locked it up in my little wall safe! I meant to, I know, but failing that, it lay there on the laboratory table and I must have come away and left it. In the morning it was gone! I searched the place over, inch by inch. This is my last chance; the authorities will never get over this." His head sank down in his hands. "Where is the laboratory and how is it built?" "It is at the side of the house, and was originally a stable till we had it concreted inside and out. Solid six feet of concrete doors, ceiling--everything. "Hullo! Concrete everything? How do you see in it?" "Artificial light always, run by my own generator and dynamo, overhead. Only one door opens into the laboratory and that is from the drawing-room inside the house and it is guarded by a soldier. No one ever enters save myself; no one, not even among the rest of the family, save my father, knows of the nature of my work. Is it any wonder that my chief suspects me?" "Well, there's nothing to be said or done till I come down and see things for myself," said Cleek, very quietly. "Will there be any difficulty in your admitting me into the laboratory, by the way?" "Not a scrap. I shall just say you are another colleague----"