"Right. Balloons drift as they please and anyway none has been reported. The same is true of airborne mists or floating devices. They would hardly have such a localized effect to begin with; that seems to rule out air or sea propagation, at least in the general sense."
"You mean except for agents coming by air or sea?"
"Exactly! Let's look at the air entry possibilities. The Russian air lines are now running regular over-the-pole flights that land here, but our customs people are quite strict and our mechanics help to service their planes. I doubt if they'd take a chance on bringing in stuff that way."
"What about freighters docking here or in New Westminster?"
"A very good possibility, but here too they have to evade customs and harbor police, and with the occasional seaman jumping ship to claim political asylum, the RCMP must keep a close watch on the movements of the crew. I think we have to rule this out."
"Then the only other way is agents coming overland; but that doesn't make sense," she objected. "Why would they come all the way out west, or if they sneaked in from Mexico, why start the epidemic up here in the north where we are so much stricter?"
"I don't believe these agents came by land, for the reasons you've mentioned. I believe they come in by sea."
"You mean by submarine?"
"No, although that would seem likely at first thought. There have been too many reports, in the last few years, of unidentified submarines off the coast. The Royal Canadian Navy and the United States Coastguard and Navy are watching all the time. It would be too big a risk." I stopped for emphasis. "You must remember Dr. Hallam's second postulate. The first was that this is a war. The second, that it is a hidden war. The presence of submarines along the coast would almost certainly cause suspicion ... and that must not be, if the war is to succeed."
"Then I give up, John. How else could it be done?"