"Old Perk" stormed and raged and the detective captain in charge fumed and fussed, but nothing came of it all. One was as powerless as another. Finally the conference adjourned. The next morning in the mail, Perkins Ferguson, president of Schefert Engineering Corporation, received a letter carefully printed in rubber type. It read: Thanks for the $50 bill. You cheated us by $99,950. This will never do. Don't be like that. You poor fools, you make us increase our demand. We double it. Leave $200,000 for us on your desk and leave the desk unlocked. We will get it. Every time you ignore one of our demands, one of your number will die. Better take this matter seriously. Last warning. Invisible Death. "Not another dime will they get out of me," mused Ferguson. He started opening the rest of his mail. A clerk entered and handed him a telegram. It read: "Damon Farnsworth struck down at breakfast table. Family heard humming sound as he fell from his chair. Removed to Medical Center. Skull reported fractured. May die. "William Devins, Chief of Police, Larchmont." Ferguson wildly seized the telephone. "Get me Farnsworth's house at Larchmont!" he shouted to his operator. * * * * * The phone was answered by Jones, the butler. "This is Ferguson." An agitated voice replied: "'Ow sir, yes sir. It's true, sir. 'E was bleeding at the 'ead, sir. Something 'it 'im." "Let me talk to Mrs. Farnsworth." "They are at the 'ospital, sir." "One of the boys." "Both are at the 'ospital, sir." "Do you think he will live?" "An' 'ow could I say, sir?" Ferguson called the Medical Center. They permitted him to talk to a doctor and a nurse. The nurse referred him to the doctor, who said: "He is unconscious. There is a wicked fracture at the base of the brain. He was struck from the back--a club, I believe. He may die without regaining consciousness. I am hoping he will rally and that he will be all right." Ferguson ordered his car and, with Lees at his heels, jumped in the tonneau. He heard a humming sound back of him. He looked back and saw nothing. Both he and Lees were too impressed for words. "Step on it," Ferguson ordered the chauffeur. "Drive us to the Medical Center." At the world's largest group of hospitals, Ferguson's worst fears were confirmed. The patient was reported sinking. * * * * * Ferguson, giant of Wall Street, was a low spirited man as he drove back down town to his office. With Lees he passed through the outer offices, buzzing with business and the click of typewriters. Not a head was raised from a desk or machine. It was a well-drilled force. Into his private sanctum he walked or rather dragged himself, and wearily he sat down. He pushed a pile of papers from him and ran his hand over his hot brow. Blood pounded at his temples.