It took him a minute or two to get the exact bearings of the instruments. At headquarters he was entirely familiar with the rheostat, wheat-stone bridge, polarized relays, pole changers and ground switches, but the station outfit was not so elaborate, the in table being provided only with the old relay key and sounder. His finger on the key, tapping the double danger challenge for attention, Ralph felt himself seized from behind.

With a whirl he was sent spinning across the room and came to a halt, his back against the out table, facing Grizzly. The latter had returned to the operating room suddenly and silently. His dark, scowling face was filled with suspicion.

“What’s this? Aha, I know you!” spoke the operator. “How did you come here?” and he advanced to seize the intruder. Ralph read that the fellow guessed that he was trapped. There was a dangerous gleam in his eyes, and the young railroader knew that he was in a dangerous fix.

One hand of Grizzly had gone to his side coat pocket, as if in search of a weapon. His shoulders egan to crouch. He was more than a match for Ralph in strength, and the latter did not know how soon his comrade Mason might return.

Ralph was standing with his back to the operating table. He put his hands behind him, quietly facing Grizzly, and let his right hand rest on the key. Carefully he opened the key and had clicked west twice when, quick as lightning, Grizzly jumped at him.

“Stop monkeying with that instrument!” he yelled. “You spy!”

There was a struggle, and Ralph did his best to beat off his powerful and determined opponent, but he tripped across a stool and went flat on his back on the floor. The operator was upon him in a moment. His strong hands pinned Ralph’s arms outspread.

“You keep quiet if you know what’s healthy for you,” warned Grizzly. “You’re Fairbanks?”

“Yes, that is my name,” acknowledged Ralph.

“And you’ve been watching us, and you was put up to it. Say, how much do you know and how many have you told about it?”