In a little while, Harvey and Dr. Lurie were breathing at a normal rate. They got up and sat at the table, where Ruth had breakfast ready. "Do you think he'll come?" Dr. Lurie said. "He has to," Harvey said. "He can't afford to let anybody spread a new gospel among his people." "Would you guys mind explaining what this is all about?" growled Red Brace. Harvey laughed. "Sure, Red. It's nothing complicated; not very, anyway. Baker keeps plugging away at the fact that this is the same as living at a 27,000-foot altitude. It struck me suddenly that if that were really the case, some of us would be suffering from nose bleeds and other symptoms you get when you go up to a thin atmosphere, where the outside pressure is less than the body's blood pressure. But nothing like that has happened. So obviously, the atmospheric pressure must be about normal--the same pressure we have on Earth. There's less oxygen, but there's more carbon dioxide and there must be more of other gases, like nitrogen, to make up the full amount of pressure. "So you see where Baker figured wrong. He figured that if the amount of oxygen here is the equivalent of what exists at 27,000 feet, on Earth, then the survival time here ought to be the same as at 27,000 feet. But the analogy is wrong. At 27,000 feet above Earth, the atmospheric pressure is so light that whatever oxygen is in your blood bubbles out pretty fast. But here, where we have normal pressure, the atmosphere is pushing in on us a lot harder and keeps the oxygen in the blood longer. You follow me? "Anyway, I put all this to Doc Lurie last night and he said I must be right. So he got out some of his books and did some figuring, and what he came up with was this: If we rested--didn't move--while we breathed from our packs, getting our blood a hundred percent saturated, then we could take off the packs and go as long as fourteen or fifteen minutes before we keeled over. Long enough to convince that old buzzard that we've invented a new gimmick for giving oxygen by injection. He's up there in his palace now tearing out his hair--or more probably hotfooting this way." Red Brace leaned against the doorpost and grunted contentedly. "Boy, when I get my mitts on him." "Red," Harvey said, "this time you can get as rough as you like. I don't care what happens to him. You keep a lookout at the window. Soon as Baker gets close, everybody take off your oxygen mask and stow it out of sight. We don't want him getting suspicious about the Lurie invention. Another thing: We'll need something for him to see when he walks in the door--a box that looks as if it contains some sort of instruments." "I've got some boxes," Ruth said, going back into the bedroom. "Okay. Now, Doc, you'll do the talking, and Red and I will do the grabbing. But look casual as hell when he walks in." Ruth placed a covered box on the table. "Impressive," Harvey said. "Now, everybody, sit down and relax. It might be a long wait."