"I'm almost afraid to think, but from my past experience I think—nay, I fear—they may be spies, or agents of the Russian government."

"Spies!" cried Ned.

"Hush. Not so loud," cautioned Mr. Petrofsky. "They may even now be in hiding, especially since your aeroplane landed so near my house. They may see something suspicious even in that."

"But why should the Russian government set spies on you?" asked Tom in a low voice.

"For two reasons. I am an escaped exile, and I am not a citizen of the United States. Therefore I may be sent back to the sulphur mines. And another reason is that they may think I know the secret of the platinum treasure—the lost mine."

"Say this is getting interesting!" exclaimed Tom. "If we are going to have a brush with some of the spies of the Russian government so much the better. I'm ready for 'em!"

"So am I!" added Ned.

"You don't know them," said Mr. Petrofsky, and he could not repress a shudder. "I hope they are not on my trail, but if they are—" he paused a moment, straightened himself up, and looked like what he was, a strong man—"if they are let them look out. I'd give my life to save my brother from the awful, living death to which he is consigned!"

"And we're with you!" cried Tom, offering the Russian his hand. "We'll turn the trick yet. Now don't forget to come and see us. Come along, Ned. If I'm going to build an air glider I've got to get busy." And waving farewells to their new friend, the lads took their places in the aeroplane and were soon on their way to Shopton.

"Well, what do you think of it?" asked Ned of his chum, as they sped along at a good elevation, the engine going at half speed to be less noisy and make talking easier.