"I think so," he replied. "Up there in my space-sphere we shall be
quite safe."

* * * * *

Together they plodded silently up the sharp incline of the peak, her
hand in his. And as they went he marveled that her eyes could be so
beautiful now that the fear and horror had vanished from their
depths.

The storm clouds below had broken up and dissolved under the
increasing heat, revealing the Trap-Door City, seemingly deserted, and
the motionless black ship still resting on the plateau. Penrun turned
to the girl beside him in the control nest of the space-sphere.

"What are your friends waiting for all this time?" he asked abruptly.

"They're not my friends," she retorted. "And you might have guessed
that they are waiting for you to arrive with the other third of the
map. They are planning to surprise you and rob you of it. The entrance
to the Caves is under the edge of the Cataract over there, and by
waiting here they are sure to be on hand when you arrive. Only"--her
brows puckered in a little frown--"I don't understand why they remain
out there on the open rock after Helgers has picked a hiding-place for
the ship."

"Helgers?"

"He is the leader of the gang, and he is the man who killed that poor
old Martian aboard the _Western Star_ for the map. Helgers learned
about the treasure and the existence of the map through a convict who
was with Lozzo in the prison. Helgers pretends to be an importer in
Chicago--he actually owns a nice little business there--but in reality
he is one of the biggest smugglers in the Universe."

"How do you come to be with him?"

"I was coming to that," she replied. "My parents live on Ganymede."

Penrun nodded. He was familiar with the fourth satellite of Jupiter
and its fertile provinces.

"My father is an American, but my grandfather on my mother's side was
a Medan nobleman. He was ruined by that notorious pirate, Captain
Halkon, who descended with his ships on our city and carried off
everything of value, including the vast amount of scrip credits owned
by the state which were entrusted to my grandfather. You know the
Ganymedan debtor's law?"

He did indeed! It was one of the most infamous laws of the Universe:
ruling that the debts of the father descended to the children and
their children's children until paid.

* * * * *

"My family is now poor," she went on. "For a century or more we have
striven to pay off