"I shall certainly call on you," answered Ivan Petrofsky, "but," he added with a smile, "I think I should prefer to take my first ride in your larger airship--the one that doesn't come down so often." "Well, perhaps it is a little easier on an amateur," admitted Tom. "If you'll come over to our house at any time I'll take you out in it, or I'll call for you." "I'll come over in a few days," answered the escaped exile. "Then I'll tell you all I know of the locality where the platinum mine is located, and we can make our plans. In the meanwhile don't say anything about what I have told you." "Why?" asked Ned quickly. Mr. Petrofsky approached closer to the lads, and in a low voice said: "I am not sure about it, but of late I think I have been shadowed. I have seen strange men in the village near here and they have eyed me rather suspiciously. Then, too, I have surprised several men around my house. I live here all alone, you know, and do most of my own work, a woman coming in occasionally to clean. But I don't like these suspicious characters hanging about. "Who do you think they are?" asked Tom. "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. "Lots. I think we're in for a good time, an exciting one, anyhow, if what he says is true. But what in the world is an air glider, Tom?"