There were no traces of the intruders, however, though the two chums looked carefully about outside the building.
"You were too quick for them, Ned," said Tom. "You came as soon as I called. They heard me speaking, and must have known that I had given the alarm."
"Yes, I didn't lose any time," admitted Ned, "but I didn't see a sign of anyone as I ran up."
"They must have been pretty quick at getting away. Well, now to decide what's best to do to-night."
After some consultation and consideration it was decided to set the burglar alarms in every building of the Swift plant. Some time previous, when he had been working on a number of valuable inventions, unscrupulous men had tried to steal his ideas and models. To prevent this Tom had arranged a system of burglar alarms, and had also fitted up a wizard camera that would take moving pictures of anyone coming within its focus. The camera could be set to work at night, in connection with the burglar alarms.
The apparatus was effective, and thus an end was put to the efforts of the criminals. But now it seemed Tom would have to take new precautionary measures. His camera, however, was not available, as he had loaned it to a scientific society for exhibition.
"But we'll attach the burglar wires," decided Tom, "and see what happens."
"It might be a good plan to have Koku on guard," said Tom's chum. "That giant could handle four or five of the chaps as easily as you and I could tackle one."
"That's right," agreed Tom. "I'll put him on guard. Whew! That chloroform is giving me a headache. Guess I'll go to bed. I wish you'd stay over to-night, Ned, if you haven't anything else to do. I may need you."
"Then of course I'll stay, Tom. I'll telephone home that I won't be in."