“That cave Is it also behind the sealed steel door?”
“No. It is accessible from the main tunnel. From the left fork.”
“Describe it.”
“The storage tank itself holds seventy-five hundred liters. Roughly two thousand gallons. It is topped by a heavy access port.”
“How secured?”
“Eight bolts.”
Sig frowned. “Too much. Go on.”
“There is a series of pipes and valves that allow the heavy water to be forced to the pile in the adjoining cave under dry-air pressure.”
“The valves?”
“Standard. A gate screwed into the pipe by a stem running through the body with a turning wheel on top of the bonnet.”
“That's it!” Sig exclaimed. “That's how we get the contaminant into the heavy water. Through the valve!” He was getting excited. “How much heavy water is held in the storage tank?”
“A little better than fifteen hundred gallons.”
Sig whistled.
“You will need an agent like cadmium that would absorb neutrons,” Himmelmann mused.
“Boron,” Sig said. “Boron does just that! Boric acid. That's generally available. It's a mild antiseptic. Eyewash. It is an excellent neutron-absorber.” Quickly he pulled a pencil and a notebook from his pocket. “We could get boric acid in powder form,” he said. “It would readily dissolve in the heavy water. It would be impossible to detect without extensive tests.”
He scribbled on the paper. “I figure — twenty-five boron parts per million would screw up the works nicely.” He looked at Himmelmann. “Professor?”
“I agree,” the scientist nodded.
“One gallon of heavy water weighs 9.16 pounds. Fifteen hundred would weigh—13,740 pounds.” He calculated furiously for a moment. “Shit!” he said in disgust. “We'd have to dump in close to a pound and a half of boric-acid powder!”
“That should be no problem,” Dirk commented.
“Maybe not,” Sig said. “But buying that amount of boric-acid powder sure as hell would raise some eyebrows. Who'd need a bathtub full of eyewash?”
“I get your point,” Dirk said dryly.
“Wait! Wait just a minute!” Sig turned to Oskar. “At the yard,” he said urgently, “you have machine shops. You do a lot of welding?”
Oskar nodded. “We do.”
“What do you use as a flux?”
“Borax,” Oskar said. “That is standard. We get it from Italy.”
“That's it! Borax contains boron. It's a crystalline powder. Like salt. Or sugar. And it's soluble in water. We'd need about fifty percent more of that than of boric acid. Let's say — two pounds.”
“Can we get that much?” Dirk asked.
“Sure. Borax is widely used in welding; it promotes fusion. No one would question a couple of pounds of the stuff.” He turned to Oskar. “Can get? Okay?”
Oskar nodded. “Yes. I can get it.”
Sig looked at Dirk, his face flushed. “Dirk,” he said excitedly. “If we can get to the heavy-water storage room — and have five minutes undisturbed — we can foul up the test, and the damned Krauts won't know what hit them!”
Dirk stared at Sig. He broke into a wide grin. “Siggy baby,” he said fervently, “I love you.” He grew businesslike.
“Okay,” he said crisply. “Here's exactly how we'll do it. Same plan. We've gone over the details already. We'll simply have to make a few changes. Timing is the key to the whole thing, or it will fall down around our ears. Remember exactly what each of you is supposed to do — and when!”
Soberly they watched him He looked at each one in turn.
“At 0940 hours,” he began.
“Come on, Dirk,” Sig interrupted. “Give it to us in civilian, please!”
Dirk grinned. “Okay. The operation will start in the morning of April the tenth.” He glanced at Sig. “Is that civilian enough for you?. That gives us two full days to line up everything we need.” He looked at Oskar. “Time enough?”
Oskar nodded. “More than enough.”
“Good…. At nine forty in the morning,” Dirk continued, “Oskar and I will arrive at the railroad yard. I will have Otto's yard pass as before. Just in case. We will proceed to Signal Post Forty-nine, which is in a pretty isolated spot. We will begin the initial step of the operation at exactly nine fifty.
“At nine fifty-five Sig will enter the restricted area at Haigerloch. He will have no difficulties, using his Red Pass, God bless it! At ten o'clock Gisela will arrive in Wehrmachthelferin uniform on Anna's bike. She presents herself at the checkpoint with an eyes-only dispatch for Professor Himmelmann to be delivered personally. Himmelmann will be contacted by the guard.” He looked at the scientist. “It is imperative you make yourself available at exactly that time.” Himmelmann nodded sourly. “If the guard does not call the professor on his own, Gisela will insist Himmelmann will confirm that he is expecting the message. His assistant, Sig, will escort Gisela to the cave-entrance bunker to meet the professor….
“At ten ten Sig and Gisela will arrive at the communications center. Sig, you will overpower the guard in the lobby. Gisela — you will have to distract him so Sig can knock him out. Okay? Sig will, of course, not be armed.”
Gravely Gisela nodded.
“Okay. Oskar and I should be on our way to Haigerloch by then. And now comes the crucial point. It must be exactly on time…. At precisely ten twenty Gisela will make her broadcast over the public-address system all through the area and the caves! Got it?”
Gisela nodded soberly.
“Okay. At ten thirty we all meet at the cave-entrance bunker. Gisela, you stay outside. We go in. You know the drill from there on.” Again he looked at Himmelmann. “Don't forget, Professor. It is important that you make certain the steel door to the reactor cave area is sealed and locked! This is a change. It is vital. We do not want to be able to get to the pile itself — or the instrumentation where we could do real damage: But — they must think we tried! They must think we hadn't counted on the locked steel hatch. How could we know about it? You then get out and leave the area, establishing your — eh, innocence. Okay?”
Himmelmann nodded. “I understand.”
“At ten thirty-four I will set the explosives at the steel door and in the laboratory Oskar and Sig will make their way to the heavy-water storage room They will dismantle the valve and dump the borax powder into the pipe. They will reassemble the valve and get out.”
He looked at the two men.
“And remember. Leave absolutely no trace that you have been there. That is vital!”
They nodded.
“At ten thirty-nine I light the fuses.” He grinned at Sig. “Don't worry, Siggy baby, if you are not through by then — I'll wait a few seconds! Sig and Oskar will then join me and we get the hell out of there! We'll have had twenty-one minutes. We can't stretch it any further. We can expect counter-action at any time after that.
“At ten forty-one the explosions inside the cave go off. Ought to be a real ball-slammer! We need those pyrotechnics. They must think that the explosion is the real sabotage attempt. They must not even suspect anything else. The steel door probably won't sustain much damage. We may blow a couple of hinges off…. But we'll wreck the lab. Making it that much more difficult for them to conduct tests that may reveal the contamination later on…. Main thing is — they'll be able to carry out the final test on schedule.”
He looked around at them. “If they do go ahead with the test — and I'm betting they will.” He grinned broadly.
“Good luck!”
8