Vickers hesitated. Despite the pistol in his ribs, he thought he could take the two plainclothesmen. It would be a futile move, though. The ISP would throw out the net for him, and this time he would be sent back to Jupiter for life. He sighed, "All right," and climbed into the cab. He wondered if there could be any connection between the incident outside the spaceport and this visit to ISP headquarters, but he knew it would be useless to ask. He stared silently out the cab window at the polyglot crowd, drawn from three worlds. The moon was international. It was governed by a board of seven delegates, one each from the seven great nations of Earth. They were known simply as "The Seven" with headquarters in the moon-tower near the center of Luna City. The ISP offices were located there too as well as all government bureaus. All at once Vickers realized that the cab was headed in the wrong direction. "Where are we going?" he demanded, jarred out of his stoical calm. The ISP agents had taken seats one on each side of him. He could feel their guns prodding his ribs, sleek automatics with built-in silencers. Wicked things that could tear half his guts out. "Shut up," the blond man said. Vickers lapsed into silence again. He was more bewildered and angry than alarmed. Try as he would, he couldn't guess who'd want him badly enough to snatch him. There had been no rivals in Vickers' line of work. Samuels and Rebkia, his partners, had both been killed in the ISP trap two years ago. There was no one left who had any interest in him. Unless-- He said suddenly: "You're not ISP agents." "That's right." "What's the idea then?" "You ask too many questions," said the blond man. "An' that's a fact," the other agreed. Vickers' mouth set. He still thought he could take the two gunmen, but his curiosity had the best of him. He sank back in the cushions and waited. The cab had gone about three kilometers when it pulled up at the curb. "All right, Vickers," the blond man said; "here's where you get your answers." He crawled out, straightened. The cab had stopped before a door of opaque blue plastic. Above it in letters of electric blue light was the inscription: INTERNATIONAL SPY RING INCORPORATED Secrets Bought and Sold Vickers stared at it in disbelief. There was just the plain blank door squeezed between a theatre on the right and a travel agency with posters of the Martian deserts in its windows on the left. The blue door was hard to focus on--like a slightly blurred picture. He opened his nictitating lids. To his utter bewilderment, he found himself looking through the door into the theatre lobby. The blue door didn't lead anywhere. It wasn't even a door, he realized, but an illusion! * * * * *