"All right," I said resignedly. "On your own head be it." * * * * * We trotted down the stairs and over to the parking lot. The Ferguson started easily and picked up speed quickly as the hydraulic drive fed power to the four wheels. I watched the center strip and wished for the radar control that was now being installed on the turnpikes south of the border. We didn't have it here yet so I had to rely on what little my eyes and ears revealed as we tunnelled through the fog. Over the Burrard Bridge it seemed thinner and we made better time. We dived back into the depths along Georgia and I used the curb as a guide as we curved through Stanley Park and over the Lion's Gate bridge. The tunnel would have been quicker but I wanted to see the extent of the fog. At the center of the bridge it was too deep to tell but that in itself was encouraging. We swung around the cloverleaf and on to the old West Van. road. "Where are we going? Horseshoe Bay?" Pat said quietly, as she drew on a cigarette. It was the first time she had spoken since we started. I liked that about her; she could wait better than any other woman I knew. "Yes, to the wharf." "I'd like to know why, if you don't mind telling me." "I don't mind at all. You should know," I said, and paused to reflect. "Light me a cigarette and I'll give you the whole picture as I see it." I was lining up the facts in my mind as she put the burning cigarette to my lips. "The first thing we have to do," I began, "is to assume that Hallam is right. If he is, if this is biological warfare, then how did it get started? There are several possible ways. The virus could be brought in by agents; it could be sprayed, or floated, or in some fashion sent ashore from ships or submarines; or it could be seeded from the air, either by aircraft or by something like those balloons the Japanese sent over on the air currents during World War II. Now, it started right in the city of Vancouver, so it seems to me that would rule out some of these possibilities." "The balloon theory for one," Pat murmured. "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?"