“Is it? Did you know, Ms. Wells, that when you broke up with Carver he wondered if perhaps you had your sights set on Professor Azevedo?”

  “What?” Tracy practically shouted; and at the same time I said, “Nick, that’s out of line!”

  “Oh, he was quite sure of that for a while. He said a lot of bitter things when he was drunk.”

  “Anson! You didn’t believe that?”

  “Tracy, I was hurt. I … No, I didn’t believe it, I just didn’t know what to believe. I wanted some explanation.”

  “And maybe…” Nick broke back in. “Maybe he was correct. Motivations, that’s what we’re after here. Was it perhaps the woman scorned? And that brings us back to this cable.” Nick held up the cable for us all to see. “I had Bosun Smith bring me this cable from the lab because there was one piece of information missing from our earlier report: the RFID tag woven into the cable end. And guess what? It’s not one that Professor Azevedo packed in his gear.”

  “What do you mean?”

  “Ms. Wells, the RFID tag is clear, and your meticulous inventory is equally clear: this cable came from your personal supplies. You had it stowed in your tent each night before the climb. Oh, and Bosun Smith also searched the rest of the expedition’s supplies very carefully; and the Professor’s cable is nowhere to be found. She checked the tag on every cable. Someone swapped this sabotaged cable for his.”

  Someone swapped … And Tracy had packed this cable … And …

  No. I couldn’t believe that. Tracy had surprised me before. She had disappointed me. She had broken my heart. But this? No. I knew that was impossible. I loved her, it couldn’t be possible.

  But Nick was drawing the conclusions I refused to draw. “So the cable Paolo packed, the cable that would’ve been in his tent every night where Margo had access to it: that cable’s missing. And the cable you packed, Ms. Wells: that cable’s sabotaged.”

  Tracy grew livid. “What are you implying?”

  “I’m presenting facts, not implications. Now that we’re in Earth orbit, it’s up to Mission Control to make decisions from these facts. My duty is to report what I know, not to speculate.”

  “So what will you report?”

  “The facts exactly as I know them. I will report that this cable is not Professor Azevedo’s, it is yours. I will report that it was under your control the entire time it was on Mars. Professor Azevedo’s cable is missing, and no one in the expedition crew admits to knowing where it’s at. I will report that this cable has been contaminated with salt-affixing nanomachines. And I’ll report all the rest of our findings, and they can draw whatever conclusions they may.”

  “And I will get a good lawyer to ensure that your accusations never make it into my record.”

  “I’m not making accusations. The conclusions should be obvious to anyone with half a brain, so I expect the review board to miss them entirely.”

  “And what are you going to do, Captain?” Tracy asked.

  “Nothing, and you know it. Now that we’ve passed the gravipause, my powers are strictly curtailed. I can’t hold you. I have no authority here over anyone but my crew.”

  “Well, that’s good news, because I’m innocent. As soon as the funeral’s done, I’ll clear my name.”

  I knew that determined look on Tracy’s face. Every bit of self-control was at work, holding back her anger, and maybe her tears. I wanted to comfort her, but I had to stand my post. She looked at me, and I almost broke; but then she left for the docking bay.

  No one else spoke. Mrs. Azevedo stood. She stared at Nick, her expression unreadable. Then Gale offered her an arm, and they left.

  * * *

  I stood where I was. I hadn’t been dismissed, and I had no orders, so I had nothing to do but stand there and stew over all that I had just heard. Stand and stew and stare at Nick.

  Nick ignored me for almost a minute and a half; but finally he spoke. “Don’t stand there glowering at me. Can’t you make yourself useful?”

  “‘Glowering’? Really?”

  “It’s the perfect word to describe your expression, and I get to use it so seldom. But get over it already. Ms. Wells will be fine. In fact, I’ve entered a commendation into her record.” I must have looked puzzled, so Nick explained. “The silly little girl who broke your heart is gone. That woman who just left here is the only one on that whole team who understands how to properly plan a mission. I can’t guess what changed her, but I can’t deny the change. Azevedo was an ass. He chose his expedition members for their willingness to fawn over him and for how popular they would be in the press. Plus a bunch of other entirely personal reasons: camaraderie, influence, favors … You name it, anything but competence. But with her, despite himself he got lucky. The only one whom he chose who was worth a damn was Ms. Wells, and even I wouldn’t’ve guessed that. She surprised me.”

  “What?”

  “Look at her reports, Carver. Look at what she’s done. Look at everything. Despite my doubts, that woman has shown that the discipline that we need in space can be found far outside the Corps. The people who want to go to space, the ones who really should be there, are going to do it right. I couldn’t have predicted it four years ago; but if I had to staff a mission and my choices were ‘professionals’ like Gale or an amateur like Ms. Wells, I would choose her without hesitation.”

  “But I thought—I thought you blamed Tracy! You practically accused her of murder!”

  Nick sighed, his “you are beyond an idiot” sigh. “There was no murder here, Carver.”

  “No murder?”

  Nick tapped his desk and the comm chime sounded. “Mr. Riggs, you can come in now.” The door to the outer office opened, and Riggs entered, looking nervous as usual when crewmen are summoned before Nick. I ushered him in, and he stood at attention before Nick’s desk.

  Nick wasted no time on pleasantries. He sat and looked up at Riggs, who stood neatly at attention. “Midshipman Karl Riggs … What do you know about salts in chemistry?”

  “Not much, Captain, I’ll admit. I know I like salt on my chips!” It was a weak joke, and weaker in Riggs’s delivery. Nick had the man nervous, which wasn’t unusual.

  “Ah, that’s right, you said you’re weak in chemistry. Unlike Ms. Wells, say. Quite a surprise, that chemistry degree of hers, it gave me a whole new perspective on that discovery of yours.

  “Mr. Riggs, a salt is a compound wherein a positive and a negative ion exactly counter each other, yielding a neutral end product. They can be quite useful both biologically and in other reactions, and it’s very hard for us to get by without them. That’s why we’ve manufactured nano lines that can scavenge or even assemble the necessary ions from available stock.”

  “I … see, sir.”

  “But nano machines don’t have brains, Riggs. They only have simple chemical sensors, valence detectors particularly. They look for the proper valences, grab the ions, and affix them to other ions or to a substrate. They’re really just glorified enzymes in a sense. If they can’t find the precise valence signature and yet they’re still active, some of them will grab the nearest equivalent they can find: something close enough to the right ionic properties.

  “Ah, but something close electrically can still be chemically a very different salt. For instance…” Nick pulled up Riggs’s report on his desk comp. “These nanos in these micrographs you took, they were designed to scavenge carbonate items out of Mars’s atmosphere, with its high concentration of carbon dioxide. It’s almost 95% CO2, did you know that?”

  “Well, I … I knew something like that, sir.”

  “Yes. And in fact, Azevedo chose his site because of the high presence of carbonates, perfect for these nanos. But if they can’t find the carbon ions they’re designed for, many of them will find the next closest valence. For example, a nitrite ion would be electrically identical to a carbonate ion, and a nitrate might be close enough for a nano’s detectors.

  “Now there’s something interesting about these micrographs you took. If you look at the chemical analysis attached—as I did when you brought them to me—you will find that the S3 cables have been contaminated with nitrite salts, and also a smaller proportion of nitrate salts, not carbonate salts. That means that when those nanos were active, they found predominantly nitrogen stock, not carbon dioxide. Nitrogen, you know, the stuff that makes up 79% of standard air mix.”

  Riggs was silent. His normally fair complexion had turned even more pale.

  “In fact, since they get much of their stock from the surrounding air, that implies that this contamination happened in a nitrogen atmosphere. Now you won’t find that on Mars, as I said. It’s nearly all CO2. And you wouldn’t even find it in the expedition’s shelters. They used heliox as their breathing gas to lower their payload mass. That, by the way, is why I was so insistent on confirming the details of which Mars tents were used and where and how the gear was stowed. I needed to be certain that I knew where these cables had been and what they might’ve been exposed to; and all three expedition members confirmed for me that the gear was safely stored in the Mars tents every night, in the heliox conditions. There would be trace amounts of nitrogen, surely, but it should be completely dominated by carbon dioxide. There was no chance for contamination there, so there’s only one place this contamination could have happened.”

  I couldn’t keep quiet. “On the ship!”

  “Yes, on the ship, Chief Carver. And since these cables were very thoroughly inspected and recorded by Ms. Wells—I’m quite astonished at her meticulous records, Carver, you could learn something from her—we can be certain that the cables were not contaminated when they left the Collins. And so the contamination could only have happened aboard the Aldrin—after Professor Azevedo’s all-too-avoidable death.”

  Riggs found his voice. “I … see, sir.”

  “Oh, I’m quite sure you do. And Mr. Carver is starting to see as well, though I think you had a head start on him. I knew right away: I wasn’t investigating a murder, I was investigating a frame-up. Someone is trying to frame someone for Azevedo’s death, and I needed to know who the someones were.

  “So I had to ask myself the traditional questions: who had means, who had motive, and who had opportunity? At first I thought Ms. Wells had opportunity. She could’ve gotten to the cable at any time; and once we learned it was her cable, the opportunities expanded. But no, even before that, I learned of her chemistry degree. No chemist would make that mistake with the atmospheric ions. They would know it was a waste of time.

  “As for Margo … What would she gain by making Azevedo’s death look like murder? Not much. For one thing, the spouse is always the first, most likely suspect in a homicide, especially given their well-known fights. Oh, in theory she might have tried to frame Ms. Wells by swapping the cables; but Margo had too much to lose either way. Her whole media campaign is about Azevedo’s great judgment, his people instincts that helped him to select an elite team of scientist explorers, the best of the best. If people think he let a murderer onto his crew, his entire myth falls apart. Not that I put any stock in that myth, mind you, but her investors do. She wouldn’t do anything to endanger that myth. It would ruin her.

  “And Horace?” Nick chuckled. “What would he gain out of it? Cast suspicion on Margo, maybe? Hardly. He needs her. He’s a joke in the Corps. Yes, I know he’s a bigwig to you SPs, but no one in Mission Control trusts his decisions. He needs this Civilian Exploration Program to succeed if he wants to stay employed. Oh, I considered briefly that Horace might have a motive: if Azevedo’s death was murder, then it couldn’t be blamed on Horace’s poor planning. He could’ve been trying to duck responsibility. But Horace just isn’t that clever. Besides, he may be a damned fool, but he’s well versed in the atmospheric chemistry of Mars. He couldn’t make that mistake any more than Ms. Wells could.”

  I broke in. “And that’s why you didn’t question Dr. Ivanovitch, either. You knew his chemistry knowledge ruled him out as a suspect.”

  “Yes.”

  “Then why’d you interview Gale at all?”

  Nick grinned. “Because it amuses me to rub his nose in his mistakes. And I wanted his perspective on the personalities of the expedition. Horace Gale may be a pompous ass, but he’s also a political climber. He always knows the gossip.

  “But that was before I realized I was looking in entirely the wrong direction, because I was only looking at the expedition personnel. If the sabotage happened here, that added dozens of potential suspects from our own crew. Mr. Riggs?”

  Riggs was slow to respond. “Captain?”

  “Reports are that you seem to be very friendly with Gale.”

  “Yes, sir. We … worked together in the past. I trained under him on my first post. And besides, he’s the only other Brit on board. It’s nice to talk football with someone.”

  “Indeed. My reports are that you’ve spent pretty much all of your free time with him.”

  “Can you blame me, sir? It’s a chance to talk to a real explorer. Someone different on this ship, you know.”

  “Um-hmmm. Perhaps you forget: both I and Chief Carver have already been to Mars on the second Bradbury expedition. I do hope we’re ‘real’ enough for you.” Riggs took the rebuke without blinking, and Nick continued. “And you—and you’re not alone in this, so don’t take offense—you’ve voiced concern in the past that the CEP is a mistake, and missions like this should be Corps missions. ‘Leave space to the professionals,’ I believe that’s what the SP activists say.”

  “I’m entitled to my opinion, Captain. As you say, I’m not alone. We Space Professionals have a lot of influence in the Corps command.”

  “Yes, yes, just what we need: more politics in the space program. Be that as it may … It looks like, despite poor planning and one unfortunate death, this expedition met most of their mission objectives. I would hazard a guess that Ms. Azevedo’s investors will be pleased over all, and will invest in further CEP expeditions. Once she buries her husband, Margo still has the clout and the drive and the financing to mount another expedition, and another.”

  “I wouldn’t know, sir.”

  “Oh, trust me, she does. These decisions are being made politically these days, not sensibly. And I’m sure you believe it as well.”

  “Y-yes, sir.”

  “But now if Margo were to be implicated in a murder—or for that matter, if any of the senior staff were, it hardly matters who—it would throw everything into disarray. Suddenly there would be investigations, there would be questions, there would be doubts … Investors would get nervous and pull financing. The Corps would feel pressure from the Space Professional contingent, and would likely push to cancel the CEP. The next mission would likely be under Corps command, probably under Horace Gale himself; and he would pick his loyal crew.”

  Nick still held the coil of S3 cable in his hand, looking down at it, not at Riggs. “I have a report from your supervisor that you may be leaving us.”

  “Sir?”

  “He says you’ve applied for a transfer.”

  “Well … Yes, sir, just … considering it.”

  “Yes, and a chance to ingratiate yourself with them as well, especially with Horace Gale. Looking at the letters of recommendation you’ve requested—”

  “Sir!”

  “Pshht. You think any communication goes out from this ship without me knowing about it? Please. What kind of a Captain would I be if I didn’t keep up with details on my vessel? So it looks like in fact you’re hoping for reassignment to the Mars expedition on their next trip.”

  “Well…”

  “And lo and behold, with the news from this expedition, there are sure to be some vacancies on that crew. Azevedo dead, and now Miss Wells tied up in legal battles, the whole CEP in jeopardy … There should be a complete shakeup. It’s likely the Space Professionals will get their way. Gale will end up in charge, and there could be an opening for the right man.”

  “Well, I … guess…”

  “Oh, most certainly. Horace would want to take his chosen crew with him, men he knew and trusted. And you hope to be one of them.”

  “Captain…”

  “Oh, don’t deny it. As I was told, three-quarters of my crew applied for that last expedition, you included. But there will be some difficulty with your transfer, I’m afraid.” Nick touched the comm control on his desk. “Bosun, come in, please.”

  The office door opened, and Bosun Smith came in. She carried another coil of S3 cable.

  “Well?” Nick looked from Smith to the cable.

  Smith nodded. “It was in his cabin, sir, just like you said it would be. I found it coiled up in his pillowcase, crammed in between the bunk and the wall. You’d never notice it without a search. Well, you might, Captain, but not the average person.” She handed the cable to Nick. “The RFID tag confirms: that’s Professor Azevedo’s cable.”

  Nick stood slowly, came around his desk, and stood nose to nose with Riggs. He didn’t yell. That’s when I know Nick is really angry, not just domineering: he gets very calm. He looked at Riggs and said, “Get off my ship.”

  Riggs swallowed. “Sir?”

  “You lied to me, Mr. Riggs.”

  “Captain, I—”

  “Don’t bother denying or explaining. We may be inside the gravipause; but when it comes to my crew, I am still judge, jury, and lord high executioner. And I do not want to hear more lies. I’m a realist, I know people lie for all sorts of stupid reasons. It’s part of their nature. But not to me, and not on my ship. That gets people dead, and I won’t tolerate that. Bosun, escort Mr. Riggs to his cabin. Watch him pack his kit. If he tries to go anywhere else or talk to anyone else, slam him into the nearest bulkhead. Twice. Once he’s packed, escort him to the docking bay and confine him there until the ferry arrives.”

  “Yes, Captain.” Smith didn’t grin, but her eyes did. She was half again as large as Riggs, and she knew how to fight dirty. I think she wanted Riggs to make trouble. But he didn’t: he just left, and Smith followed.