entific
Institute of this city are destroyed. A number of lives have been lost.
The cause has not been determined. It is reported that the laboratories
were beginning analytical work, on the so-called Harkness Dark Moon
gas--

"Confirmation has just been radioed to this station. Dark Moon gas
exploded on contact with air. The American, Harkness, is either a
criminal or a madman; he will be apprehended at once. This confirmation
comes from Herr Schwartzmann of Vienna who left the Institute only a few
minutes before the explosion occurred--"

And, in the quiet of a hospital room, Walter Harkness drew a long breath
and whispered; "Schwartzmann! His hand is everywhere.... And that sample
was all I had.... I must leave at once--go back to America."

He was halfway to the door--he was almost carrying Diane Delacouer with
him--when Chet's quiet tones brought him up short.

"I've never seen you afraid," said Chet; and his eyes were regarding the
other man curiously; "but you seem to have the wind up, as the old
flyers used to say, when it comes to Schwartzmann."

* * * * *

Harkness looked at the girl he held so tightly, then grinned boyishly at
Chet. "I've someone else to be afraid for now," he said.

His smile faded and was replaced by a look of deep concern. "I haven't
told you about Schwartzmann," he said; "haven't had time. But he's
poison, Chet. And he's after our ship."

"Where is the ship; where have you hidden it? Tell me--where?"

Harkness looked about him before he whispered sharply: "Our old shop--up
north!"

He seemed to feel that some explanation was due Chet. "In this day it
seems absurd to say such things," he added; "but this Schwartzmann is a
throw-back--a conscienceless scoundrel. He would put all three of us out
of the way in a minute if he could get the ship. _He_ knows we have been
to the Dark Moon--no question about that--and he wants the wealth he can
imagine is there.

"We'll all plan to leave; I'll radio you later. We'll go back to the
Dark Moon--" He broke off abruptly as the door opened to admit the
nurse. "You'll hear from me later," he repeated; and hurried Diane
Delacouer from the room.

But he returned in a moment to stand again at the door--the nurse was
still in the room. "In case you feel like going for a hop," he told Chet
casually, "Diane's leaving her ship here for you. You'll find it up
above--private landing stage on the roof."

Chet answere