ered my other questions: when do we go back?"

Harkness took the queries in turn.

"I didn't show the old boat," he explained, "because I'm not ready
for that yet. I want it kept dark--dark as the Dark Moon. I want to do
my preliminary work there before Schwartzmann and his experts see our
ship. He would duplicate it in a hurry and be on our trail.

"And now for our plans. Well, out there in space the Dark Moon is
waiting. Have you realized, Chet, that we own that world--you and
Diane and I? Small--only half the size of our old moon--but what a
place! And it's ours!

"Back in history--you remember?--an ambitious lad named Alexander
sighed for more worlds to conquer. Well, we're going Alexander one
better--we've found the world. We're the first ever to go out into
space and return again.

"We'll go back there, the three of us. We will take no others
along--not yet. We will explore and make our plans for development;
and we will keep it to ourselves until we are ready to hold it against
any opposition.

"And now, how soon can you go? Your injury--how soon will you be well
enough?"

"Right now," Chet told him laconically; "to-day, if you say the word.
They've got me welded together so I'll hold, I reckon. But where's the
ship? What have you done--" He broke off abruptly to listen--

* * * * *

To all three came a muffled, booming roar. The windows beside them
shivered with the thud of the distant explosion; they had not ceased
their trembling before Harkness had switched on the news broadcast.
And it was a minute only until the news-gathering system was on the
air.

"Explosion at the Institute of Physical Science!" it said. "This is
Vienna broadcasting. An explosion has just occurred. We are giving a
preliminary announcement only. The laboratories of the Scientific
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 whisp