Enigma by Michael P. Kube-McDowell

Thackery to think he had successfully shut McShane off. It was not to be.
    “I wonder whose dream this is. I’ve tried to make it disappear but it doesn’t.” Thackery could not be sure McShane was joking but chose to take it that way. “Neale’s, I think.”
    “Maybe.” Another long pause. “I haven’t seen her much. Do you know her well?”
    “No.” Thackery hesitated. If he’s determined not to let me sleep, then at least we can talk about what I want to talk about . “Do you see Sebright? I mean ever?”
    “The Contact Leader? No.”
    “I was asking Michael today whether Sebright had said anything to him about a briefing on the Muschynka contact. He said he hadn’t seen Sebright for three days.”
    “He’s probably sync’d to the C or D watch schedule.”
    Thackery missed the impatience in McShane’s voice. “No, because I left a message for Derrel—he’s on that cycle—and he said he hasn’t seen Sebright either.”
    “So, Sebright’s a recluse. So what?”
    “He’s supposed to be here to give us the benefit of his experience,” Thackery insisted. “We’re five days out and I can’t even find anyone who’s met with him. He doesn’t respond to pages, he doesn’t answer messages, and he’s never in his cabin.”
    “Look, I’ve got problems of my own,” McShane said irritably. “If you’ve got a real grievance, go see Neale. If you just want to complain, find some of your own people to listen.”
    “McShane, you’re a selfish son-of-a-bitch,” Thackery said tiredly.
    McShane jumped up from his bunk. “Damnit, I’m the one with responsibilities on this craze. You don’t have to stand watches. You don’t have Rogen and Graeff breathing down your neck looking for an excuse to replace you. You’re on a freezin’ vacation.”
    “Whoa, easy,” Thackery said, snapping on the light. McShane shivered oddly, hung his head, and stood a moment with arms akimbo.
    “Sorry,” he said at last. “If your problems aren’t my fault, I guess mine aren’t yours, either.” He sighed expressively and settled back on the bed. “He’s got a single, doesn’t he? Break his damn door down and wait for him. He’s got to show up there sometime.”
    Thackery laughed tiredly. “Unless he’s moved in with some little awk from Tycho .” He turned out the light and turned on his side. “Who knows,” he said to his pillow, “maybe that’s what I ought to be concentrating on, too.”
    For two days, Thackery shifted Sebright to the back of his mind. In that time, he made a token (and profitless) attempt at courting Jessica Baldwin, got off to an encouraging start on his studies for the exobiology qual, and solved the first test message Eagan had composed for him.
    But on one of his many trips from the passenger hive upship to the Tycho library, he cast a glance as always from the climb-way down the corridor onto which Sebright’s door opened—and saw a woman he did not know push that door open and disappear inside.
    For a moment Thackery was torn by ambivalent impulses. Then impatience won out over propriety, and he stepped off the climbway and stalked down the short corridor.
    But there was no answer to the page button, no answer to his insistent knock. “Concom Sebright,” he called out, listening for sounds beyond the closure. “This is Merritt Thackery. Can I talk to you?”
    There was no answer, no sound at all. Frustrated, Thackery smacked the door release with a balled fist and began to turn away. But the door, which had been locked every time he had been there before, slid open.
    Sebright was lying prone in the narrow single cabin, his ankles strapped in a microgravity exercise cradle and one hand gripping the crossbar. Beads of perspiration stood out on his cheeks and forehead, and the longish hair was matted. But his eyes were closed, as though he were sleeping. An instant later, Thackery saw why: The fingertips of Sebright’s right hand were in the grasp of a small black box