brought in. But we pay off only once a year. That way I'm not burdened with guarding money the whole year around. I have well over fifty thousand credits in the safe now. And tomorrow I begin paying off."

"Then we'll have to be ready for him," Hawkes said, "though I don't expect him until tonight. Probably just about the time you're ready to close. He'll need you to open the safe. I can count on your help?"

Johnson nodded.

hat night as they waited in his office, Johnson turned to Hawkes. "I've been giving some thought to what you told me this afternoon about the robberies. I have a theory that might account for some of the things we don't understand."

"Yes?" Hawkes looked closely at Johnson.

"You've probably heard of our tourist attraction called Nature's Moebius Strip? As far as we know, no one has ever gone beyond a certain point—and returned. Suppose there's a time flaw at that point—and the bearded man has somehow learned about it. Suppose anyone completing the Moebius circle, and returning, finds—say, twenty years have elapsed, while to him only a few minutes have passed?"

"Go on." Hawkes leaned forward intently.

"He makes his first holdup," Johnson continued, "and goes around the Strip. When he comes out twenty years later they're no longer looking for him. He leaves Marlock, and during the next five years he goes through the money he stole. He returns and repeats the process. This time the money lasts only three years. Now he's back to try it again. Do you see how that would tie everything up in a neat little package?"

Hawkes smiled, as he relaxed and sat back. "A bit too neat," he said. "Also, you don't have an ounce of concrete evidence to back up your theory."

"That's right. I don't," Johnson agreed.

Outside the door a board creaked. Johnson glanced quickly across the room to where Hawkes sat with a pistol on his lap. Hawkes' eyebrows raised, but he made no sound.

uddenly the door was kicked open and the black-bearded stranger stood framed in the doorway. "Raise 'em!" he barked. The gun in his hand was aimed at Johnson.

The man took two steps into the room. Hawkes shifted slightly in his chair and the gunman's head swiveled in his direction. The slug from Hawkes' pistol made a small blue hole in the upper left corner of his forehead.

The thug's face tipped up, shocked and unbelieving. He swayed slowly before he fell backward, his body rigid. His fur cap flew from his head as he struck the floor.

"I thought we'd better play it safe," Hawkes said as he rose and walked over to the fallen man. He slipped his gun into his pocket before he bent and picked up the cap at his feet. He dropped it over the upturned face.

For a long moment the silence held thin as the two men looked at each other. Hawkes stood, wiping his right hand on his trouser leg. Johnson toyed idly with the gun he had picked up from the desk in front of him.

Finally Hawkes let his body sag into a chair at Johnson's right. "This is always a dirty business," he said sourly.

Johnson sat down also. "Did you notice the look on his face when he saw you, and you shot him?" he asked, abstractedly turning the pistol in his hand. "Funny thing. In that half-second before he fell an article I read somewhere flashed into my mind. It seems that during the French Revolution a certain doctor got to wondering just how long a man's brain remained active after his head had been cut off. He persuaded some of his friends who were due