She walked out into the entrance hall without a backward glance, opened the front door and shut it very firmly behind her. She was glad that Roger had not offered to see her to the elevator or to accompany her to the street and put her into a taxi. She had a great many things to be grateful for. And she wished--she wished that she were dead. * * * * * It was six days after Helen Lathrup had been found slain in her office by Lynn Prentiss that Ruth Porges found the murder weapon. She stumbled upon it by pure accident, in a place where the police hadn't looked and would scarcely have thought of looking. That she found it at all was due to one of those almost unbelievable blind flukes which fiction writers prefer to shun, but which persist in occurring, with surprising frequency, in real life. She not only found the weapon--a black metal, long-barreled forty-eight calibre pistol equipped with a silencer--but she knew immediately who the owner of the gun was, precisely when and how it had come into his possession, and hence, by inference, who the murderer had to be. Unless, of course, someone who was not the murderer had loaned the gun to someone else. And that seemed unlikely, since a man or woman owning such a gun would know exactly how it had been used and would have gone immediately to the police and cleared himself of all suspicion by naming the borrower and explaining the circumstances under which he had allowed himself to be made an unwitting dupe to the one crime in which a taste for silence could lead straight to the electric chair. Ruth Porges found the gun in a sixty-foot-deep excavation. In New York City, there are many scenic beauties and intricate works of engineering construction which can be said to be typical of the city as a whole. Every city has them, of course, but some cities are famous for their numerous bridges and reservoirs, or high stately office buildings, or parks and playgrounds, or triple-laned speedways, or museums and schools. New York, Pittsburgh, Chicago and San Francisco all shine in that respect, along with perhaps fifty other cities from coast to coast. New York is a city of bridges, of course, the most beautiful bridges in the world, if you're willing to waive the Golden Gate. It is also a city of equally beautiful parks and its cluster of tall buildings is second to none. But New York, in recent years, and perhaps more than any other city in the throes of a refurbishing and a reconstruction, of a tearing down and a putting up, is a city of excavations. Everywhere there are excavations, three or four blocks apart, deep and yawning and carefully encircled by board fences to keep absent-minded people from falling into them in the dark or even in broad daylight. Some are one hundred percent walled in and others are open a little on one side and are hence a menace to the unwary and should painstakingly be avoided if one does not wish to die.