Sandy shrugged. They went into the ship, which Holmes had already reached and where he sat gloomily beside a black cube. He would have to sleep to get anything from it. There were only two of the freakish-seeming metal caps which made the cubes intelligible to a man awake, and Burke and Keller were using them. Holmes felt offended.
Sandy looked at a clock and began to prepare a meal. Pam, brooding, helped her.
Burke and Keller came back to the ship together. Keller looked pale. Burke seemed utterly grim.
"There's some stuff to be coded and sent back to Earth," he told Sandy. "Keller's got it written out. We know how to work the instruments up above, now. My brain's reeling a little, but I think I'll stay sane. Keller takes it in stride. And we know the trick the Enemy has."
Sandy put out plates for five.
"What is it?"
"Gravity," said Burke, evenly. "Artificial gravity. We don't know how to make it, but the people who built this fortress did, and the Enemy does. So they've made artificial-gravity fields to give their ships the seeming mass of suns, and they've set them in close orbits around each other. They'll come spinning into this solar system. What will happen when objects with the mass of suns—artificial or otherwise—come riding through between our sun and its planets? There'll be tidal stresses to crack the planets and let out their internal fires. There'll be no stability left in the sun. Maybe it'll be a low-grade nova when they've gone, surrounded by trash that once was worlds. Anyhow there'll be no humans left! And then the Enemy will go driving on toward the other solar systems that the builders of this fortress own. They can't conquer anything with a weapon like that, but they can surely destroy!"
Keller nodded distressedly. He gave Pam a number of sheets of paper, filled with his neat handwriting.
He said sorrowfully, "For Earth. In code."
Sandy served the meal she had prepared.