Dan looked around at the gray walls, with shelves stacked to the low ceiling with wrapped paintings. Two three-hundred-watt bulbs shed a white glare over the tile floor, a neat white refrigerator, a bunk, an arm-chair, a bookshelf and a small table set with paper plates, plastic utensils and a portable radio--all hastily installed at Kelly's order. Dan opened the refrigerator, looked over the stock of salami, liverwurst, cheese and beer. He opened a loaf of bread, built up a well-filled sandwich, keyed open a can of beer. It wasn't fancy, but it would do. Phase one of the plan had gone off without a hitch. Basically, his idea was simple. Art collections had been disappearing from closely guarded galleries and homes all over the world. It was obvious that no one could enter a locked vault, remove a stack of large canvases and leave, unnoticed by watchful guards--and leaving the locks undamaged. Yet the paintings were gone. Someone had been in those vaults--someone who hadn't entered in the usual way. Theory failed at that point; that left the experimental method. The Snithian collection was the largest west of the Mississippi. With such a target, the thieves were bound to show up. If Dan sat in the vault--day and night--waiting--he would see for himself how they operated. He finished his sandwich, went to the shelves and pulled down one of the brown-paper bundles. Loosening the string binding the package, he slid a painting into view. It was a gaily colored view of an open-air cafe, with a group of men and women in gay-ninetyish costumes gathered at a table. He seemed to remember reading something about it in a magazine. It was a cheerful scene; Dan liked it. Still, it hardly seemed worth all the effort.... He went to the wall switch and turned off the lights. The orange glow of the filaments died, leaving only a faint illumination from the night-light over the door. When the thieves arrived, it might give him a momentary advantage if his eyes were adjusted to the dark. He groped his way to the bunk. So far, so good, he reflected, stretching out. When they showed up, he'd have to handle everything just right. If he scared them off there'd be no second chance. He would have lost his crack at--whatever his discovery might mean to him. But he was ready. Let them come. * * * * * Eight hours, three sandwiches and six beers later, Dan roused suddenly from a light doze and sat up on the cot. Between him and the crowded shelving, a palely luminous framework was materializing in mid-air. The apparition was an open-work cage--about the size and shape of an out-house minus the sheathing, Dan estimated breathlessly. Two figures were visible within the structure, sitting stiffly in contoured chairs. They glowed, if anything, more brightly than the framework.