his queer actions--I--I----"

Words failed the youth. Throwing wide open the door, he sprang out of
the projectile. A moment later there dashed into the yard, where the
great projectile rested, a strange figure astride of a puffing
motorcycle. The figure was torn and, ragged, and the nondescript
garments were covered with dust, for Mark had had a fall. But there was
no mistaking the face that peered eagerly forward.

"Jack!" cried the youth on the machine.

"Mark!" ejaculated the lad who had sprung from the projectile. "What
has happened? Who is the fellow who has been masquerading as you?"

"A scoundrel and a villain! Let me get at him!" and, slamming on the
brakes, as he shut off the power, Mark leaped from the motorcycle,
stood it up against the projectile, and clasped his chum by the hand.

"What's the matter?" asked Professor Henderson, as he, too, ran out of
the _Annihilator_. "What does that tramp want, Jack? Give him some
money, and get back in here; we ought to have started long ago." He
looked at the ragged figure.

"This isn't a tramp," cried Jack. "It's Mark!"

"Mark! I thought----"

"There have been strange doings," gasped the lad in tramp's garments.
"I have just escaped from being kept a prisoner. Where is the
mysterious man? Oh, I'm glad I arrived in time! Were you about to