"Maybe," Rick said, grinning. "That cable doesn't sound like anything soft." Steve got serious. "You two proved yourselves in Washington, so far as I'm concerned. You can make yourselves useful, and you'll provide a good cover for Zircon." "What kind of cover?" Barby asked. Steve smiled at her. "Women can't keep secrets, I'm told." "I can," Barby retorted swiftly. Steve held up his hand for silence. Hartson Brant had Zircon on the line. The scientist outlined Steve's proposal in a few words, and gave Zircon the contents of Chahda's cable. Then he listened to Zircon while Rick fidgeted anxiously. Finally, Hartson Brant said, "All right, Hobart. Tell your people up there that I'll take your lectures. We'll see you later today." He hung up and nodded at Steve. "Hobart had lectures scheduled for next week, but I can take them for him. He'll be down this afternoon, and, he says, he'll be ready to leave in the morning if necessary." "Good!" Steve nodded at Barby. "Even if you can't go on the trip, you can make yourself useful. Want to place a call to Washington for me?" "Yes," Barby said eagerly. "Where to?" Steve gave her the number. Then, while she was placing the call, he said, "Now, I'll tell you what I know." Rick's heart beat faster. Now he would learn what was behind Chahda's cable! "The day before I phoned here," Steve began, "my office received a message from Carl Bradley. It was a top secret message sent to us via the American consulate general's channels from Singapore. I'd better explain first that Carl is a JANIG man. His knowledge of that part of the world has made him invaluable, and he works for us secretly while doing his routine work as an ethnologist. That is top secret information that must never be repeated outside this room." "You can depend on us," Hartson Brant assured him. "I know it. To go on. His job is gathering information about persons who show too much interest in operations within our embassies and consulates. However, the cable we got from him wasn't quite in that line." Steve paused to see how Barby was getting along. She was trying to listen to him and the operator at the same time. "This cable," Steve continued, "said he had accidentally made a discovery of something potentially dangerous to America. He asked for a competent nuclear physicist, and he named you, Hartson, to be sent to Singapore at once to check on his finding, and to locate, if possible, the source of the stuff he had discovered. We haven't heard from him since. From Chahda's cable, it's evident something has happened to him. And on the basis of the cable, I think we'll send Zircon and you boys to Hong Kong first." Scotty put into words the question that was in Rick's mind. "What was it that he discovered?" Steve's lips tightened, then he said: "_Heavy water!_" CHAPTER IV Project X "Heavy water!" Hartson Brant exclaimed softly. Rick and Scotty looked at each other blankly.