Slim smiled and snapped a bunch of switches. The lights in the tubes went out. “Think what this will mean in criminal prosecutions, to be able to follow a man in the past. Present-day testimony will be archaic. The courts won’t have to take anybody’s word for anything; they can follow a man and watch him in the past.”

“Judge Monday wouldn’t admit that kind of evidence,” I pointed out.

“Naturally not. It will take twenty-five years to get this kind of evidence admitted in court. In the meantime, we’ll have to go easy. But we can make millions, just by bluffing. When we know that a man was playing poker in Jones’s basement until six o’clock Sunday morning, then we can bluff and put it over. Just so we don’t tangle with a real tough guy the first time. For instance⁠—sh! Somebody’s at the door.”

Slim ran to the door while I ran for my pants. I ducked back into the other room and got them on. I heard the voice. It was a man’s voice, and I had heard it before⁠—just recently. I peeked out. Yes, it was Tom Ellingbery. I stayed quiet.

“A potbellied little guy just served divorce papers on me,” he said harshly. “I got off the train and came here. A friend of mine sent me; I want your services.”

“Yes,” said Slim.

“Here’s a hundred-dollar bill,” Tom Ellingbery said. “Start shadowing my wife; get something on her. I’ll give you five thousand to get something⁠—ten if it’s necessary,” he said with a slight leer.

Slim gravely picked up the C note. “We don’t do business that way,” he said; “but if your wife has been misbehaving we’ll find it out.”

Ellingbery was a big man with a sharp go-getter look about him. He stared hard at Slim and Slim stared back. Ellingbery’s expression didn’t show anything; then he left.