he walked across the roof, estimating the distances with practiced ease, as if he'd undergone extensive training and the apprenticeship period had been forgotten and only the skill remained. he knelt and fused two small rods to a portion of the roof, and then readjusted the torch and cut a small circular hole. he listened, and when there was no alarm, lifted out the section. there was nothing but darkness below.

he fastened a rope to the aircar. he dropped the rope through the hole and slid down. unless he had miscalculated, he was where he wanted to be, having bypassed all alarm circuits. there were others inside, he was reasonably certain of that, but with ordinary precautions he could avoid them.

he flashed on a tiny light. he had guessed right; this was memory lab—the room he'd wanted to see this afternoon but hadn't been able to. in front of him was the door to the waiting room, and beyond that the hall. he swung the light in an arc, flashing it over a desk and a piece of equipment the nature of which he didn't know. behind him was still another door.

the desk was locked, but he took out a small magnetic device and jiggled it expertly over the concealed mechanism and then it was unlocked. he went hurriedly through papers and documents, but there was nothing with a name on it. he rifled the desk thoroughly and then went to the machine.

he didn't expect to learn anything, but he might as well examine it. there was a place for a patient to sit, and a metal hood to fit over the patient's head. he snapped the hood open and peered into it. it seemed to have two functions. one circuit was far larger and more complicated, and he couldn't determine what it did. but he recognized the other circuit; essentially it was a retrogressor, but whereas the gun was crude and couldn't be regulated, this was capable of fine adjustment—enough, say, to slice a day out of the patient's life, and no more.

that fitted with what had happened to luise. she had been experimented on in some way, and then the memory of that experiment had been erased. but the man had grown careless and had taken away one day too many.

he snapped the mechanism closed. this was the method, but he still didn't know who the man was nor why he found it necessary to do all this.

there was a door behind him and the answer might lie beyond it. he listened carefully, then swung the door open and went through.

the blow that hit him wasn't physical; nothing mechanical could take his nerves and jerk them all at once. a freezer. as he fell to the floor, he was grateful it was that and not a retro gun.

lights flooded the place, and the man of the afternoon interview was grinning at him.

"i thought you'd be back," he said, pleased. "in fact, i knew you would."