"I'm not sure," Joe answered seriously. "We know the comet's tail is so rarefied that it resembles a pretty fair vacuum, but it _is_ composed of something. As it mixes with the atmosphere we ought to be able to determine the changing makeup of the air and get a pretty good idea of the composition of the comet's tail. This is a chance nobody's ever had before--and maybe never will again, until we go right out there in spaceships--being right inside a comet's tail long enough to analyze it!" "It sounds like a terrific project," Ken admitted. "The universities will all be doing it, of course, but it would still be a neat trick if we could bring it off. Maybe Dad and Professor Larsen will have ideas on how we could do it." "We ought to be able to make most of the equipment," said Joe, "so it shouldn't be too expensive. Anyway, we'll have a meeting then, right after school?" "Yes--no, wait. The engine in my car conked out. I've got to go over to Art's with it this afternoon. You go ahead without me. Kick the idea around and let me know what's decided. I'll go along with anything short of mortgaging the football field." "Okay," said Joe. "I don't see why you don't just sell that hunk of junk and get a real automobile. You've got a good excuse now. This breakdown is a good omen!" "Don't talk to me about omens!" * * * * * Art Matthews had the best equipped garage in town, and was a sort of unofficial godfather to all the hot-rodders in the county. He helped them plane the heads of their cars. He got their special cams and carburetor and manifold assemblies wholesale, and he gave them fatherly advice about using their heads when they were behind the wheel. Ken called him at noon. "I've got troubles, Art," he said. "Can I bring the car over after school?" "I'm afraid I can't do a thing for you today," Art Matthews said. "I don't know what's happened, but I've had tow calls all day. Right now the shop is full and they're stacked four-high outside. I'm going to do a couple of highway patrol cars and Doc Adams'. I figured they ought to have priority." Ken felt a sudden, uneasy sense of recognition. This was the same kind of thing he had heard about on the radio that morning! A rash of car breakdowns all over the country. Now, the same thing in Mayfield! "What's wrong with them?" he asked the mechanic. "Why is everybody coming in with trouble at the same time?" "They're not coming in," said Art. "I'm having to go out after them. I don't know yet what's wrong. They heat up and stall. It's the craziest thing I've run into in 30 years of garage work." "Mine acted the same way," Ken said. "Yeah? Well, you're in good company. Listen, why don't you and maybe Joe and Al come down and give me a hand after school? I'll never get on top here without some help. After we get these police and other priority cars out of the way, maybe we can get a quick look at what's wrong with yours." "It's a deal."