He threw off the thought and replaced it with another; in the process, no doubt, merely exchanging hostilities. Professor Slocum could be overconfident about the American vigilance. He, Duff Bogan, could have been right about his tests. People — suspicion-proof people like Harry Ellings — could be busy on a project calculated to go far in overthrowing the freedom of the world. Somebody would have to investigate further, even if it was only an overtall, underweight, overworked, badly dressed graduate student named Allan Diffenduffer Bogan.

“I don’t know what to do, exactly,” Duff said later in the day to Mrs. Yates, who had listened patiently to his story. “I can keep following Harry, of course. If he has a secret date with that big guy again — that darn-near giant — I can try to follow the big man when he leaves cover. I’m a lousy follower, though.” He grinned. “One of my many hobbies wasn’t being a boy detective. Or even trailing animals in the woods. I never did make a good Boy Scout.”

Mrs. Yates smiled maternally. “I can imagine. Poor Duff.”

“Oh,” he hurriedly protested the pitying sound. “I had my compensations, remember.

Best stamp collection in town. I could send Morse Code, as I taught the kids and Eleanor.

Pick locks and do escape tricks. I was the best slingshot marksman in the county.”

She nodded and sighed. Her eyes rested on him wonderingly. He was twenty-four now, she thought. An age when lots of men had homes, jobs, families. But Duff was a sort of split personality. Half of him was stuck in his childhood and his innumerable boyish interests. The other half, abstract, precocious, was far ahead of most of the college boys brought home by Eleanor.

“Why don’t you,” she suggested, “go see that Mr. Higgins and tell him about Harry’s meeting? He seemed very shrewd, from the glimpse I had.”

Duff’s long head shook slowly. “Not me! Not again! Not until and unless I can tell him something that’ll really convince him.”

“You afraid, Duff? False pride? Or what?”