David is gone for three days, leaving her with nothing but a crackling voice on her headset to distract from her thoughts. The first day, he makes regular and scrupulously precise reports, emerging every two hours or so to give her readings and a description of the terrain. He describes to her the codes to every door (hook, rising stroke, falling stroke, upward diagonal, downward diagonal, chevron, small o, great O) and their distance as they radiate out from the main hallway. (The dais is their agreed-upon point of reference for all distances; she's used to working in cave systems that are only partially charted, but she's also used to working with full safety precautions, a full crew of teammates sweating and joking and a Thermos of coffee waiting at the mouth of the tunnel. David is alone.) The second day, his reports come less regularly, and he seems to have doubled back on his exploration. The third day, he does not report back at all without her prompting.

On the third day, Shaw is without the willpower to practice her lessons, or to check the console and study the projections. She can't even get up from where she'd curled up to sleep, and it's certainly not because her uniform is too cosy (no more close calls there) or the massive control chair is too comfortable. Her joints ache, she feels clammy and too-hot. The thought of getting sick out here, months from any destination even in an incomprehensibly advanced alien craft, is unbearable. She had hope still, a cold necklace tucked against her collarbone like a charm, and she had an aim, but that wasn't enough to banish dread of the worst.

The temperature has dropped by a degree or too, and she doesn't know why. All she can think of is their frightening vulnerability -- her with her chills and draining incision, David's head isn't fixed back on as securely as it should be, he may have increased tolerance to extreme climates but he is not immune to sudden changes in temperature or pressure. Whatever had eaten through Milburn's helmet would have no difficulty cutting through David. She isn't frightened for him, exactly (should she be?) but she is frightened.

Elizabeth had lost her mobile phone once -- it seems horrid, simplistic, to compare those machines that seemed more and more like their organic counterparts every day with a device she could leave behind at a party and wake up the next day without. She had the presence of mind to take something for her hangover and to shuffle home, then shredded a deep gouge in her calf when she'd stumbled on the kerb -- but she couldn't get into her hall of residence with neither keys nor sticker to scan, couldn't phone for help and could only sit there, flat on her bottom and clutching the thing with mucus running from her nose, until someone with a working pass showed up. She had even reached toward her pocket for something to distract from the pain -- as if it would have materialized there when she wasn't looking. It shouldn't have been overwhelming, but something in her had just broken. At the blood running down her socks and pooling in her shoes, at the sudden and embarrassing pain from such an ordinary origin, at just how useless she was without a computer to prop her up. And now she was a grown woman, dependent on an electronic device in a thin polyurethane coating that was not only possibly fragile but possibly hostile.

David had merits, he was indispensable, and his peculiar company had become familiar to her. It was low-level stimulation, if nothing else. But if he became a crutch, something she'd die without, what became of her should he opt to just leave her here? To betray her somehow when they arrived at their destination, or even long before then. He could taint her water supply -- she was left rationing the reservoirs from Meredith Vickers' support unit, and if worst came to worst there was a damp trickle down the wall that had promise. (So saith David.) But there was no guarantee that that would even be safe to wash with, let alone drink, and filtering it might mean destroying the filter itself. She could have resorted to drinking her own urine, but it was a little late to start on that. David might seek to satisfy his intellectual curiosity by trying out some new microbe or fungus he found down there on her. He could be sending a distress beacon right now to the Engineer home world to warn them about this puny intruder. For evidence of his fidelity she only had -- what? His gratitude, his word as an ownerless, malfunctioning piece of machinery.

Perhaps he's already abandoned her. Maybe he's fallen down a hole somewhere. Maybe his signal's been cut off. God only knew -- maybe he has simply grown distracted by something inscrutably delightful.

Shaw unfolds herself and sits up, feeling a nauseating head rush that makes her ears ring, and fumbles for her communication link. Her fingers are numb inside her gloves.

"David? David, can you hear me?"

Her voice is cracking. It sounds strange in her own ears. David is the way he always is -- a little distorted in transmission, but calm and mild.

"Yes, ma'am."

"Tell me about the wildlife, David," she says, a little wary of what she'll hear but desperate to hear something.

"Many new varieties of arthropod at every stage of development, including one that appears to be bioluminescent. I'll refrain from taking samples," he says, dryly. "Large annelids, and some form of nesting mammal. None of the overtly hostile life forms found on the other ship. I suspect these are the descendants of their vermin. Several of their sleep chambers contain Engineer remains, but these were their civilian staff, Dr. Shaw."

"Any sign of anything immediately hazardous? Any remains? Any more of those cylinders?"

"That's an interesting question."

"Then it deserves an interesting answer. David, are we safe enough to travel?"

"Certainly. I'm returning to base tonight, by seven o'clock. There's no need for distress. I believe I've found something for you."