 With each succeeding development, the air mail mystery gets more and more difficult to solve. The Department of Justice has assigned Miss Irene Delroy and her assistant Fitzgerald to find out why trans-American airlines have lost three of their very latest high-speed mail planes in mysterious crashes within a month. In each case, a valuable shipment of bonds and securities was found to be missing when the wreckage of the plane was located. Andy Andrews, veteran pilot of trans-American, is flying east with the night air mail. Miss Delroy, Fitzgerald and Jimmy Gifford, roving newspaper reporter, have just made the astounding discovery that there is a plot to wreck the plane in which Andrews is flying and rob the mail compartment of a shipment of currency. The radio operator at Salt Flats is trying desperately to reach Andrews' plane by radio. Salt Flats calling Andrews in 655. Salt Flats to Andrews in 655. Go ahead. Salt Flats to Andrews. Go ahead. I can't get him, ma'am. Not a word out of him. Do you think he might be out of range of your transmitter? Not likely, ma'am. Might be skipped distance, though. Want me to try him through metropolitan? I doubt if he'll be able to reach him, but you might try. I'll try to get him through metro. Salt Flats to metro. Salt Flats to metro. Go ahead. Trying to raise Andy in 655. We're afraid he's in trouble. Try to get him from there, will you? Go ahead. When he was talking to you, he said his motor's cut out over nothing. Looks like we've lost another ship and maybe a pilot. Fitz is probably right, Irene. But all we can do is hope that Andrews sets that plane down on the floor of the canyon, OK? No use, Miss Delroy. Well, there's only one thing to do. That is to get to the canyon as quickly as we can. Andrews may need help. Fitz, did you turn Pirelli over to the airport police? Yeah, I told him to book him on suspicion and not let anyone near him. Not even a lawyer. Good. Tell our pilot to get the ship warmed up, Jimmy. We're leaving for Devil's Canyon right away. I'll tell him. Tell him that we may need some parachute players, too. I'll tell him right away, Irene. Lawrence, tell Metro we're flying to the spot where Andrews is last heard. Keep in touch with us and we'll relay orders through your station. Yes, ma'am, but it's pretty risky business flying to the canyon tonight, ma'am. Andrews' life may be at stake. It's not a question of risk, but a question of rights. Yes, ma'am, but take it easy. Don't take any chances. I'll keep you posted on the weather. We'll be at the canyon in an hour. Radio Metro that we're leaving. Comfort. Yes, ma'am. Hurry, Fitz. They're warming the ship up. I don't like the idea. Open the door, Jimmy. All right, Fitz, climb up on the pilot. Yes, ma'am. Tell him to cut to the left to Guadalupe Peak. We're missing the beacon, but we're taking the shortcut. All set, Jimmy? Right. All set, Fitz? Yes, ma'am. Yeah, we're almost there, ma'am. There's the beacon on Central Hill. Straight ahead. Tell the pilot to nose down and drop a flare, Fitz. Yes, ma'am. Here goes the first flare, ma'am. On my side, Irene. Over here. Look. We're over the canyon all right. Fitz. Yes, ma'am. Ask the pilot if he thinks he can land in the canyon. Yeah. If you're still raw, I want to know if you think you can land in the canyon. Well, he says it's pretty risky business. He'll try it, though, if you want him to. Tell him to go ahead and fly to land. Tighten your safety belt, Jimmy. Wow. Won't I have a story if we go through this? Say, he's diving it. Drop another flare, Fitz. Yes, ma'am. There she goes. We're down on the canyon now, Jimmy. Look. There's a clearing. Get ahead. Yeah, we're going to try for that clearing, ma'am. I think I see Andrew's ship down there. Where, Jimmy? Right over there. It's the left of the flare. Look. It looks like the ship all right. And it's not wrecked. How are we coming, Fitz? OK, ma'am, so far. We're clear of those rocks back there. Hold it. He's leveling off. We made it. We're down. Boy. That was one of the biggest thrills of my life, Jimmy. Who says these trans-American pilots don't know their stuff? We've got to get to that ship as soon as possible. Hurry, Fitz. Yes, ma'am. I have a feeling that all this isn't as it should be back there. Come on, Jimmy. We'll need you, too. OK. It's just around this bend. Look, there's the ship. It isn't hurt. Not even the landing gear bent. That's luck. Come on. Just a second, Fitz. Wait. Oh, what's wrong, ma'am? Do you see Andrews anywhere about? Well, no, ma'am. That's what's puzzling me. If Andrews set the ship down as safely as he did, it should be somewhere around. He wouldn't go away and leave the mail. That's right, ma'am. I think it'd be better if we moved up rather cautiously. Maybe a trap of some sort. You don't want to take any chances. Yes, ma'am. I'll go ahead. I have a hunch that something's wrong, I mean. I don't know why, but I have. I feel the same way about it, Jimmy. Let's follow Fitz. I'm glad I brought a gun. Wouldn't have much chance to use it, though, with all these rocks around here. Fitz is walking up to the ship now. Andrews mustn't be about. Come on. Andrews did a sweet job of landing this plane with a dead motor. Hmm. We'll have to take the ship out here on a truck and never be able to take off out of this canyon. It's not humanly possible. Right, Jimmy. See anything, Fitz? No, ma'am, not yet. The baggage compartment's open. The baggage compartment? Yeah. Yeah, and the mail compartment's open, too, ma'am. The lock's broken. There's mail all over the ground over here. Look. See if Andrew's bag is in the baggage compartment. Is it a traveling bag, ma'am? Yes. Uh... Or... No, ma'am, it ain't. There's nothing here. Oh. Just what I thought. Andrews was implicated in this, if he wasn't the actual leader of the gang. He set the ship down here, took the money shipment, and skipped out. Yeah, you were wrong this time, Gifford. Look at this. What is it? What does it look like? Blood. That's right. Blood. There's been a fight of some kind here. It's... What, ma'am? That blood is coming from directly under the cockpit. I wonder... Oh, look, ma'am. Uh, give me a hand up, Gifford. Right, Sergeant. Here you go. Uh, that's enough, Gifford. Let me down. Is it? Yes, ma'am. Andrews, he's slumped forward in the seat. Well, let's get him out quick. I'll give you a hand, Sergeant. No use, Gifford. He's dead. Dead? Well, this isn't a crash. I don't see how he could... Looks like our robbery case has turned into a murder, Miss Delroy. I was afraid of that, Fitz. Is it very bad? Pretty bad, ma'am. Andrews is shot through the head. Oh! You're sure he's... Nothing we can do, ma'am. Somehow I hold myself to blame for this, Fitz. I shouldn't have let him... You did all you could, ma'am. You radioed him to turn back. He didn't listen. Oh, I shouldn't have allowed him to take that money shipment out on the run tonight. Fitz, this is the last straw. We're working day and night until we solve this case. If they wreck the mail lines, they may start on the passenger ship. It our duty fits to stop any further development. Well, let's get busy. Yes, ma'am. What first, ma'am? Take a good look at the cockpit. See if Andrews' gun is in its holster. No, ma'am. It's on their floorboard. Is the bullet hole in the front or in the back of his head? The front, ma'am. Square between the eyes. Probably a 45. Is the ignition switch off? Yes, ma'am. His safety belt. Is it unfastened? Yes, ma'am. That's all fit. What do you think, Irene? It's very plain what happened, Jimmy. Andrews came in here for a landing. He set the ship down safely, cut a switch, unfastened his safety belt and started to get out. Someone came up alongside the ship. Andrews reached for his gun, but it was too late. And then? Whoever shot him came around to this side of the ship and tried the mail compartment open. It's broken the bags until he found the shipment from the bank. Then took Andrews' traveling bag out of the baggage compartment and left. What did he want with Andrews' bag? Oh, there are a lot of questions that remain to be answered, Jimmy. Which brings us back to our original question. What is that? Why did these ships go haywire in the first place? What makes the motor stop right over this canyon? That's another thing we're going to find out before we leave. We have a whole ship to examine this time, not merely a massive wreckage. I need to have that motor examined piece by piece. There's a reason why that motor stopped over this very spot and I intend to find it. You're too late, ma'am. I already found it. What? You mean you know why the motor cut out on Andrews tonight? Yeah, and I know how the job was done. Look over here, ma'am. You see this thing here? Yes, what is it? It's a booster magneto, ma'am. You use it to give a hot spark to start the ship. Well? Well, this one ain't really a booster mag, ma'am. Look, it's just a shell. See what I found inside? A time clock. Sure. See, that's how it was done. Someone who had access to this ship put this time clock in the ignition circuit. The time was set for the exact number of minutes required to take the plane out over this canyon. Then the clock clicks, the contact snaps, and the motor isn't getting any spark. Sergeant, you'd hit the nail right on the head. You solved that part of the case. A time clock, eh? In the ignition circuit. Well, what do you know about that? What was that? Look, there's fire. Quick, quick! Right under the ship, you see? They planted a small magnesium bomb under the gas tank. It was time to go off and run the ship before we got here, but we beat him to it. We can't stop that fire, ma'am. It's spreading too quickly. Give me a hand, Giverd, so we can get Andrews out of that cockpit. Okay. This ship will go up like thunder. Hurry! I may be just a flat foot to you, Giverd, but I got a pretty good idea who started this fire, and I'm going to run him down.