The Shark waved them back. “Here! Don’t walk all over a fellow!” he cried. “What I saw—or thought I saw—was a head. I had just a glimpse—there one instant, gone the next—presto, change business! Looked like a human head.”

“You said it was a man’s,” Sam reminded him.

“Well, it might have been a boy’s—I couldn’t make it out clearly, you understand. It was vague, shadowy.”

“Then, of course, you didn’t recognize the face?”

“No,” said the Shark. “And you’ll understand, too, that I don’t insist that I really saw anything. You know, these glasses of mine—chance of freak of refracted light—all the rest of it. What’s the good, though, of getting all stirred up about it? If anybody was outside, he’s far enough away now. I’ll bet he’s running yet if he heard the crowd galloping out after him. Sit down, Trojan! You haven’t won a game.”

Walker plumped himself into a chair. “Well, you are a cool hand!” he said, with a touch of admiration. “But I’m going to beat you this time, all the same. Whose move is it?”

Step lounged across the room, but the others stood watching the play, which went on briskly, and to the advantage of the mathematical genius. The Trojan, beaten rather disgracefully, pushed back his chair.

“Tackle him, Poke,” he urged. “Or you take him on, Sam. This isn’t my night, I reckon.”

Poke grinned. “Age before beauty! Go ahead, Sam.”

But there was to be no more checker play in the club just then. For, while Sam paused, debating his chance of coping with the skilful Shark, there was a loud crash of a breaking window pane, a little shower of fragments of glass fell to the floor, and a big stone shot across the room, just missing the boys standing by the table, which it struck with great force. Over went the table with a crash, rivaling that of the window. Over, too, went the Shark, untouched but thoroughly startled by the bombardment.