"What is that?" asked Greg. "A mechanical detective," said Russ. "A sort of mechanical shadow. While you were busy with the stock market stunt, I made several of them. One for Wilson and another for Chambers and still another for Craven." He hoisted and lowered the one in his hand. "This one is for Stutsman." "A shadow?" asked Greg. "Do you mean that thing will trail Stutsman?" "Not only trail him," said Russ. "It will find him, wherever he may be. Some object every person wears or carries is made of iron or some other magnetic metal. This 'shadow' contains a tiny bit of that ridiculous military decoration that Stutsman never allows far away from him. Find that decoration and you find Stutsman. In another one I have a chunk of Wilson's belt buckle, that college buckle, you know, that he's so proud of. Chambers has a ring made of a piece of meteoric iron and that's the bait for another machine. Have a tiny piece off Craven's spectacles in his machine. It was easy to get the stuff. The force field enables a man to reach out and take anything he wants to, from a massive machine to a microscopic bit of matter. It was a cinch to get the stuff I needed." Russ chuckled and put the machine back on the table. He gestured toward it. "It maintains a tiny field similar to our television field," he explained. "But it's modified along a special derivation with a magnetic result. It can follow and find the original mass of any metallic substance it may contain." "Clever," commented Greg. Russ lit his pipe, puffed comfortably. "We needed something like that." The red light on the board snapped on and blinked. Russ reached out and slammed home the lever, twirled dials. It was only another passenger ship. They relaxed, but not too much. * * * * * "I wonder what he's up to," said Russ. Stutsman's car had stopped in the dock section of New York. Crumbling, rotting piers and old tumbledown warehouses, deserted and unused since the last ship sailed the ocean before giving way to air commerce, loomed darkly, like grim ghosts, in the darkness. Stutsman had gotten out of the car and said: "Wait here." "Yes, sir," said the voice of the driver. Stutsman strode away, down a dark street. The televisor kept pace with him and on the screen he could be seen as a darker shape moving among the shadows of that old, almost forgotten section of the Solar System's greatest city. Another shadow detached itself from the darkness of the street, shuffled toward Stutsman. "Sir," said a whining voice, "I haven't eaten ..." There was a swift movement as Stutsman's stick lashed out, a thud as it connected with the second shadow's head. The shadow crumpled on the pavement. Stutsman strode on. Greg sucked in his breath. "He isn't very sociable tonight."