you should realize that we didn't have to let you fellows in on the plot and by doing as we have, we may be jeopardizing our own safety."
"I appreciate that," the slave answered. "But if you can't help us in the getaway, perhaps you can give us a suggestion or two as to how we can help ourselves."
"Gladly," Sullivan responded. "I notice that there are several Martian airmobiles parked near the stables. It ought to be a simple matter for you fellows to commander these ships and fly to Menfol. Perhaps you already know that Zurek keeps his slaving space-craft here. If you work fast, you ought to be able to surprise Zurek and his band of blackguards. There must be someone among you who knows how to operate a space-ship. How about it?"
"I used to be a pilot for the Solar System Space-Freight Corporation," one of the men said.
"And I am a graduate space navigator," another whispered huskily.
"There you are!" Lieutenant Sullivan exclaimed. "Are there any other questions?"
The five men shook their heads and Sullivan went on, "Hail, Earthmen! Each of you take three of these guns and hide them under your garments. Remember you are the appointed leaders and the fate of all your companions depends on how well you do your parts. And now—good hunting to all of you!"
"Good hunting to you, Lieutenant!" they murmured in unison and slinked back to their sleeping places.
When they had left, Hawkins, who had of course remained behind, said, "Any special instructions for me, Jim?"
Ignoring the question, Sullivan asked, "Do you know Ingeborg Andersen?"
"Never met the lady," Hawkins answered. "But her name sounds interesting. Who is she?"
Before Sullivan had time to answer this question. Ensign Mayer did it for him: "She's the daughter of Lars Andersen, the Christian missionary on Ganymede. Together with some native Ganymedians she was abducted about a week ago. We have reason to believe that she was brought here."
"That's quite possible," Hawkins told him. "A new bunch of slaves arrived the day before yesterday. I believe that part of them were Ganymedians. Perhaps Miss Andersen was among them. I was working in the wok pastures at the time so I couldn't be certain. Why do you ask about her in particular?"
"She's the one we came here to save," Mayer replied.
"A very special friend of Dan's," Sullivan explained.
"I see. Sorry I can't help you locate her," the captain deplored.
"Our most important job is to find Ingeborg," Mayer stated. "Do you mind if I hunt for her now, Jim?"
"A. Z," the lieutenant consented. "But you must be very careful. The work horn is liable to sound almost any minute now, and you mustn't let any of the Martian guards see you."
"I'll be careful," the ensign promised as he started the almost endless task of minutely examining the faces of the innumerable sleeping slaves.
While he was doing this, Sullivan told Hawkins about the invisible space-ship and the luminous blaze-marks which he hoped would guide them back to it.
"Try to get as close to this building as you can before you give the signal," he directed. "Dan and I will be hid-
