"They were burning these!" cried Ned. "You can smell the smoke yet. They came here to destroy some papers, and we surprised them!"
"I believe you're right," agreed Tom. "The ashes are still warm." And he tested them with his hand. "They wanted to destroy something, and when they found we were here they clapped the blazing stuff into the safe, thinking it would burn there.
"But the closing of the doors cut off the supply of air and the fire smouldered and went out. It burned enough so that it didn't leave us very much in the way of evidence, though," went on Tom ruefully, as he poked among the charred scraps.
"Maybe you can read some of 'em," suggested Ned.
"Part of the writing is in German," Tom said, as he looked over the mass. "I don't believe it would be worth while to try it. Still, I can save it. Here, I'll sweep the stuff into a box, and if we get a chance we can try to patch it together," and finding a broken box in what had been the factory office the young inventor managed to get into it the charred remains of the papers.
A further search failed to reveal anything that would be useful in the way of evidence to determine what object the three men could have had in hiding in the ruins, and Tom and Ned returned to the tank.
"What do you think about them, Tom?" asked Ned, as they were about to start off once more for the cross-country test.
"Well, it seems like a silly thing to say—as if I imagined my tank was all there was in this part of the country to make trouble—but I believe those men had some connection with Simpson and with that spy Schwen!"
"I agree with you!" exclaimed Ned. "And I think if we could get head or tail of those burned papers we'd find that there was some correspondence there between the man I saw up the tree and the workman you had arrested."
"Too bad we weren't a bit quicker," commented Tom. "They must have been in the factory when we charged it—probably came there to be in seclusion while they talked, plotted and planned. They must have been afraid to go out when the tank was walking through the walls."