Captain Future 12 - Planets in Peril (Fall 1942) by Edmond Hamilton

they can endure the most extreme conditions of cold and hardship, they have one hidden weakness in their makeup that would render them vulnerable to extermination by anyone who knew it.
    " 'So I am going to destroy them and try again, in order to develop a different mutant of less malignant type who will not possess this dangerous and vulnerable weakness.' "
    Lacq paused a moment, and then went on earnestly.
    "That is what my ancestor Zuur wrote in his last letter. It was the Cold Ones he was writing about, and whom he meant to destroy. He never did so, however. The Cold Ones must have guessed their creator's intention — for they killed him first. Then they spread out from Thool, increasing in numbers and invading all the universe."
    Captain Future felt a growing excitement.
    "This vulnerable weakness or the Cold Ones to which Zuur referred — was there no hint of its nature?"
    Lacq shook his head.
    "No, there was not. I searched through all the surviving papers of Zuur which my family possessed, but without success."
    "Lad, if we could learn that secret, vulnerable point, we could destroy the Cold Ones!" exclaimed the Brain.
     
    LACQ'S head bobbed.
    "That was my plan! I reasoned that the secret might exist in records made by Zuur in his laboratory at Thool. If I could find and search Zuur's records there, I would hold power to eliminate forever the menace of the Cold Ones.
    "But how was I to get to Thool to make such — a search? It seemed impossible, for distant Thool is now the capital of the Cold Ones' power. On that forbidding, icy world far across the universe lies the central city from which their king reigns. How could I reach and search that world?
    "I decided that my only chance lay in subterfuge. I would become an ally of the Cold Ones, a supposed traitor to my own race. In that way, I might be able to reach guarded Thool.
    "But though they accepted me as an ally because of false information I gave them, the Cold Ones would not permit me to go to Thool. Then you came and captured me, Kaffr."
    Curt Newton asked a keen question.
    "Even if you had got to Thool, how could you have much hope of finding the secret of the Cold Ones' vulnerability? Wouldn't Zuur's laboratory and records be gone, after all this time?"
    "No, the laboratory of my ancestor Zuur still exists on Thool," Lacq asserted. "I learned from the Cold Ones whom I 'joined' that the laboratory is still there. I gathered that the creatures shun that place of their creation. They say the place is haunted by terrible danger."
    Curt Newton's gray eyes gleamed.
    "Lacq, I believe your story. And I think it gives us the chance I've been looking for. The chance to devise a weapon with which the Tarasts can hurl back the Cold Ones for good!"
    Gerdek looked doubtful.
    "You think the Cold Ones really have such a vulnerable weakness? But what could it be?"
    "I haven't an idea," Curt admitted. "But Zuur knew what it was. He created the Cold Ones; he knew more about them than anyone else. If we could go to Thool and search his records —"
    "Go to Thool?" Gerdek repeated. "You talk as if it were easy! Do you think you can just speed to Thool in this ship without trouble?"
    "I suppose it wouldn't be easy," Captain Future conceded. "But we've got into some tightly guarded places before this."
    "You don't know of what you speak," Gerdek said emphatically. "You would not have one chance in a million of reaching Thool. That icy world lies far across our universe, countless leagues away.
    "All those vast spaces and their dead suns and worlds are patrolled and inhabited by the Cold Ones. Their ships are everywhere. You'd never get through."
    Shiri nodded troubledly.
    "And even if you did by some miracle win through the Cold One patrols, you'd find Thool so guarded that you would be discovered and seized almost at once," she warned.
    "I am afraid they are right," Lacq said discouragedly to Curt. "No Tarast ship for centuries has succeeded in even getting near Thool. It