Where was I? Oh, yes, back in Katanga. From there I wired the University that I would be unable to give my last two lectures of the semester. The Congo dateline on the telegram must have raised the shaggy brows of the venerable Chancellor who till then thought I was no farther away than my rooms at the opposite end of the campus. Armstrong I had cabled immediately with the information about MacRoberts. I was sure that while I marked time in Africa he would be Starting the chase in far-off British Columbia. Still, the waiting made me restive, and more so when after leaving Leopoldville I lost another day. Engine trouble forced the _Constellation_ down at Accra, where foul weather closed in to keep us grounded. Finally back in Washington, I ticked off another day on the pocket calendar. Only seven days more. I went directly to the _Statler_ where Armstrong had his rooms. He greeted me enthusiastically, ordered up some drinks, and plunged right into business. "Arnold, thanks to the lead you picked up in the Congo, we have a good idea where Chetzisky is." Armstrong unfolded a map with places circled in red and notations scribbled in. "He is somewhere in this area north of Ootsa and Burns lakes. Trappers in the region have identified his photograph. Also we've traced some significant shipments into the area. Paraffin, boron-steel, graphite among other things." They were significant; they were all materials that could be used in an atomic reactor, principally as moderators to control the neutron irradiation. "Any word of MacRoberts?" I asked. Armstrong gave me a quick briefing on the Canadian geologist. Single, fairly well off, Ian MacRoberts spent his summers away from his teaching chores at the University prospecting for minerals, chiefly in one of the least explored portions of the continent, the Rocky Mountain Trench. A transport lost there in 1940 has never been found. Notes found in MacRoberts' lodgings in the Vancouver suburb of Kerrisdale revealed he had discovered a strange new mineral of marked radioactivity. He made his first find near Lake Babine and traced outcroppings of it as far south as lower California. From his fragmentary data MacRoberts was convinced that a vein of this mineral dipped through the earth's crust at an inclination of 27.6°. Six months ago he had been given a leave of absence from the University; since then he had been seen twice in the company of a man fitting Doctor Chetzisky's description. Information indicated both had headed for the Interior. "Well, Jim, what are your plans?" "I have arranged already for groups of searchers to move secretly out of Prince George and Hazelton." His pencil slid over the map. "But you're the key man, Arnold; these groups will only close in on the word from you.