“God grant that we are in time,” he whispered. “Let’s see.” He turned the other tubes about. “Three labeled, and three unlabeled. We’ve got to get that man. We’ll set a watch but he may suspect, may escape us. He——”

A step sounded in the hall. Jimmie dodged as if to miss a glass bubble. Tom clicked something, in his pocket.

It was only the landlady. “He’s that wild lookin’ at times,” she murmured. “What is there to be done?”

“Nothing at present,” Tom Howe replied in as steady a tone as he could command. “We’ll have him watched.”

“Will ye, now?” The woman heaved a great sigh of relief. “May Heaven bless ye fer that now.”

It was impossible for Jimmie to read Tom’s thoughts as they left the place. His own feeling was one of intense relief. He had faced the Bubble Man once and had heard his sharp order: “As you are.” His gas bubbles had been harmless then. But what about now?

“I have something I want to do tonight,” Jimmie said to his father late that afternoon.

“For how long?” His father gave him a sharp look.

“All night.”

“I hope,” his father’s face took on a worried look, “that you’re not going into anything dangerous. You know, son, we can’t help worrying about you when we don’t know where you are, mother and I.”