The dawn sun was still out of sight far down below the eastern lip of the world. Not even the first faint glow of its coming could be seen in the sky. On the tarmac of Eighty-Four's field three powerful Mark 5 Spitfires were being warmed up and mothered by mechanics as though they were infant babes in arms. Off to one side, Dave Dawson, Freddy Farmer, Barker, and Squadron Leader Markham, stood waiting and talking of everything under the sun except the special patrol that was soon to get underway.

That was a taboo subject with them. It was for the simple reason there wasn't anything else to discuss. All the plans and preparations had been made. Special high speed cameras, that could be operated from the control stick, had been fitted in the planes. The cameras had been tested and found to be in perfect working order. Each pilot had taken his plane aloft and tested it until he was thoroughly satisfied with every beat of the engine, and every single response to a touch on the controls. Everything that could be done, had been done. There was nothing to do now but wait for the engines to be warmed up ... and then get on with the job.

"Say, Barker," Dave suddenly broke a minute's silence. "Meant to speak to you about this, but we've all been pretty busy. I mean.... Well, darn it, you're still senior officer, and I'm perfectly willing for you to take over command of this show. Fact is, I think it would be a sensible idea. I...."

"Oh, no you don't, Yank!" Barker cried and laughed. "Decent and mighty sporting of you, old bean. And I like you a lot for saying it. But I've been in command of special shows before. Not at all to my liking. Hate responsibility, you know. I'm always getting things messed up something terrible."

"Yeah, I can guess!" Dave snorted. "He's won the Distinguished Flying Cross, and bar! And he says he'd mess things up? Nix on that line, friend. But I really am serious about your...."

"Don't be!" Barker said firmly. "I refuse, flatly. No, my lad. I'm going to tag along obeying orders on this show. And love it, I fancy."

"Then you won't...?" Dave started again and hesitated.

"No!" Barker repeated. "Absolutely not. If it's a success then you get perhaps the Victoria Cross, my lad. If it's not, then you get Squadron Leader Markham on your neck. I don't! See what I mean, old thing?"

Dave grinned and looked at his commanding officer who was shaking with laughter.

"Don't mind Barker, Dawson," the O.C. said. "He's an awful one for juggling the truth. Frankly, I've never so much as spoken a harsh word to him since he's been in the squadron."

"But, what you've thought, sir!" Barker said and laughed. "Just the same, Dawson, this is your show. And in my opinion you certainly deserve to have command."

"Well, I still don't know about that," Dave said with a shrug. "But.... Hold everything! That's a ship coming down to land, isn't it?"

All eyes were turned on the star studded sky overhead whence had come the sudden sound of airplane engines. An instant later the sound died down to a purr. And a brief moment after that the darkness was cut by the twin beams of the incoming plane's landing lights.

"Can't see for those darn lights," Dave grunted. "But she sounds to me like a Blenheim."

"It is!" Freddy Farmer echoed. "I can see her, now. I say! That's the same bus Group Captain Ball, and Colonel Trevor, came down in from London. I wonder if they're coming back."

"I wonder, too!" Squadron Leader Markham echoed. And Dave thought he caught just a faint trace of hopefulness in the O.C.'s voice. "Maybe they've decided to wash-out the patrol. Maybe something else has popped up."

As Dave watched the shadowy blur slide down toward the surface of the field, then level off and settle gently, a conglomeration of mixed emotions surged through him. One instant he experienced the familiar eerie tingling at the back of his neck that was always an advance warning of danger just ahead. Then in the next instant a sense of disappointment would flood through him. As though that plane was bringing word that the flight over occupied France had been called off. Then again he was filled with the strange excited feeling of more mystery being added to what already existed. A jumble of emotions and crazy thoughts that plagued him as he waited for the pilot of the Air Ministry Blenheim to taxi up to the line.

When the plane stopped, and the door was popped open, only one man jumped down onto the ground. That man was Colonel Trevor, and he hurried over to the group with a look of marked relief quite visible on his face in the pale glow shed by the two or three flare lights set about on the tarmac.

"Thank heavens, you haven't taken off yet!" the Intelligence officer cried. "Didn't want to waste time trying to get you on the phone. Raid on in London, anyway, and the phone service isn't so good at such times. No, not a hot raid. Just a few Jerry ships up there. And our lads are handling them very nicely. Anyway, I dashed out to Croydon in the blasted black-out and commandeered Ball's plane. I've got a bit more information for you, Dawson. By the way, do you know that terrain between Boulogne and Lille?"

"Fairly well, sir," the Yank R.A.F. ace replied. "I've done quite a bit of flying over that section, now and again. Why, sir?"

The Intelligence officer didn't answer at once. He fished a hand into the pocket of his tunic and pulled out a folded sheet of paper. Smoothing it out he held it to the light so that all could see. A map had been roughly drawn in pencil on the paper.

"A map of a three square mile spot of ground exactly seven miles west of Lille," Colonel Trevor said, and started pointing things out with his finger. "See this? A hill range. Here is the Lille River that flows into the Somme farther south. See this sharp bend in the river? Well, the ground there is thickly wooded, and to the east ... the southeast, rather ... is quite an expanse of swamp ground. Now, just a shade east of the edge of that swamp land is a tiny French village. You can't even find it on a map, but its name is Fleurville. Somewhere in that area, Dawson, is the secret weapon that Hitler plans to use against us. The weapon, I am sure, that destroyed those Lockheed Hudson bombers last Tuesday night."

Dave didn't say anything as the Intelligence officer stopped speaking. He stared hard at the pencil drawn map in an effort to stamp every little detail on his mind. Squadron Leader Markham, however, was not so interested in the map as he was in what Colonel Trevor had said.

"Why do you say that, Colonel?" he asked. "And where did you get this map?"

"I traced that map from one you could only see under a microscope," the other said. "From a map originally drawn almost pin head size by my brother."

Dave jerked his head up, eyes wide.

"Your brother, sir?" he gasped. "But your brother's dead! You mean another communication came through just the same? That he'd sent it on its way before h............