"Queer chap," he murmured to himself, as he lit a fresh cigar and selected a comfortable chair in the deserted smoking-room. "He's certainly in love with her all right, but it's strange that he should have used me to put her off to-night like that. Wonder what it means." * * * * * Two hours later a wild-eyed, breathless servant bareheaded in the pouring rain, was stammering incoherently to a police-constable in Grosvenor Gardens that Mr. Robert Grell had been found murdered in his study. CHAPTER II The shattering ring of the telephone awoke Heldon Foyle with a start. There was only one place from which he was likely to be rung up at one o'clock in the morning, and he was reaching for his clothes with one hand even while he answered. "That you, sir?"... The voice at the other end was tremulous and excited. "This is the Yard speaking--Flack. Mr. Grell, the American explorer, has been killed--murdered ... yes ... at his house in Grosvenor Gardens. The butler found him...." When a man has passed thirty years in the service of the Criminal Investigation Department at New Scotland Yard his nerves are pretty well shock-proof. Few emergencies can shake him--not even the murder of so distinguished a man as Robert Grell. Heldon Foyle gave a momentary gasp, and then wasted no further time in astonishment. There were certain obvious things to be done at once. For, up to a point, the science of detection is merely a matter of routine. He flung back his orders curtly and concisely. "Right. I'm coming straight down. I suppose the local division inspector is on it. Send for Chief Inspector Green and Inspector Waverley, and let the finger-print people know. I shall want one of their best men. Let one of our photographers go to the house and wait for me. Send a messenger to Professor Harding, and telephone to the assistant commissioner. Tell any of the people who are at the house not to touch anything and to detain every one there. And Flack--Flack. Not a word to the newspaper men. We don't want any leakage yet." He hung up the receiver and began to dress hurriedly, but methodically. He was a methodical man. Resolutely he put from his mind all thoughts of the murder. No good would come of spinning theories until he had all the available facts. For ten years Heldon Foyle had been the actual executive chief of the Criminal Investigation Department. He rarely wore a dressing-gown and never played the violin. But he had a fine taste in cigars, and was as well-dressed a man as might be found between Temple Bar and Hyde Park Corner. He did not wear policemen's boots, nor, for the matter of that, would he have allowed any of the six hundred odd men who were under his control to wear them. He would have passed without remark in a crowd of West-end clubmen. It is an aim of the good detective to fit his surroundings, whether they be in Kensington or the Whitechapel Road.