“You all right, Kim?” He was standing over her, pulling on his clothes, obviously worried.

“I’m fine,” she said.

There was another, more likely, possibility.

She sat down at the console and replayed the visuals from Solly’s helmet imager, stopping the display when the ripples appeared, on the hull and in the air lock.

The thing she’d seen was connected with the saddle. The object had not been a bomb; it had been a transport.

If that were so, she wondered whether she and Solly could even talk to each other without being overheard. Had the celestials mastered enough of the language to eavesdrop?

She told Solly what she thought.

“Okay,” Solly said. “We’ll proceed on the assumption we’ve got an intruder. That would explain what’s happening to Ham as well.”

“There is this,” she told him. “At least it won’t try to murder us in our sleep.”

“I don’t want to be downbeat on this, but why not?”

“Because it wants to follow us home.”

“Kim, I hate to point this out.” He lowered his voice. “The course is already set. If it were to get us out of the way, all it would have to do is sit tight and ride old Ham into port.”

They were sitting on the bed, staring out into the corridor, which now seemed like strange territory, a passageway from another world. “No,” she said. “It probably doesn’t know what leg of the trip we’re on. It’ll want us functioning until we get home. Until it can be sure.”

“I hope.”

In the morning, they searched the vessel again, all three floors, the engine room, the lander, and every other space they could think of. Solly removed the various access panels and peered back among the cables and circuits. They found nothing. “It’s hard to believe there’s anything on board that shouldn’t be here,” he said.

Reluctantly, she said what they both must have been thinking: “Maybe we shouldn’t go home.”

They were sitting in the wingback chairs in the briefing room. It was late afternoon; both were exhausted from the long hunt and its accompanying frustrations. “Kim,” said Solly, “we can interrupt the flight anytime and call for help. But then what do we do? If it could get aboard without our seeing it, it’ll do the same to any rescue ship.” He rubbed his eyes. “We’ve done everything we can to ensure there’s no intruder. So either we go home, or we sit out here somewhere until the food runs out.”

During the search, Kim had sensed that he was becoming skeptical of her story. In full-daylight mode, the Hammersmith’s rooms and corridors seemed less threatening and the danger more remote. The choices, should they determine they actually had an intruder, were stark. Best to write the incident off as the result of dim lighting, heated passions, and too much alcohol. “Look,” he said, “at worst, all we have to do is maintain control of hypercomm, don’t let it transmit anything, and we don’t have to worry. No matter what else happens.”

“Are we sure we can do that?”

“I can take a wrench to it if I have to.”

The return trip remained somber. Kim kept their bedroom door closed, for whatever good that might do. It was, she complained to Solly, like sleeping in a haunted house. The days passed without incident, but Kim knew the thing was there, drifting through coils and corridors, just outside the range of vision. Occasionally, she caught glimpses of it, the eyes sometimes formed of light from a lamp, of steam from a shower. There were movements in the dark, the sense of a cold current brushing her ankle, the sound of whispering in the bulkheads. Even the murmur of the ship’s electronics occasionally sounded malevolent.

If Solly picked any of this up, he said nothing.

Unavoidably, the sex became infrequent. When it did occur, it was distracted, stealthy, hurried, as though there were others in the ship who might happen on them at any moment.

The spontaneity drained away. During what she had already begun to think of as the good old days, encounters might begin and eventually be consummated anywhere in the ship. Now, wherever they might start, they concluded behind the closed doors of their sleeping compartment. After Kim had put on the light and inspected it.

She felt exposed and vulnerable when they were both asleep. But when she broached the subject to Solly he looked so dismayed that she did not push for a watchstanding system.

He must be thinking of her as a frightened child, wondering what sort of relationship he’d got himself into. But she felt like a frightened child. Were their places reversed, had it been Solly who was seeing things in empty corridors, she would certainly be rethinking the relationship. She feared she might lose him over this, and that might be the worst of it. But she couldn’t help herself. There was a hazard, and Solly didn’t entirely believe her.

She grew resentful, of Solly, and of her own fears. And she acquired an unrelenting hatred for the thing that had taken up residence with them. She waited, and literally prayed, for it to show itself in some substantive way.

Solly’s efforts to get the AI back online produced no discernible results. Occasionally there were nonsense voice responses, asserting that passengers should prepare for acceleration, or that the food preparation system was suffering from an overload and needed a new conduction unit. It suggested course changes and adjustments in mission parameters and wished them good morning at all hours.

“We need somebody who knows what he’s doing,” Solly grumbled, but he never stopped trying.

Without Ham, he had to get his hands dirty on occasion. He found himself performing routine duties such as managing power flow adjustments. Because some systems had gone down with the AI, he wasn’t necessarily alerted when malfunctions happened, nor was there a system to tell him the nature of the problem. So when internal communications crashed, he needed several hours and a lot of crawling around on hands and knees to locate and replace a faulty relay. Self-test procedures run regularly by the jump engines developed an aberration that periodically set Klaxons sounding throughout the ship. He couldn’t figure that one out at all and simply shut the alarms down, hoping the engines wouldn’t develop a fatal flaw in the meantime.

Solly commented that he was learning a lot this trip.

Kim helped wherever she could, which wasn’t often. Electronics was not her forte, but she asked questions and she too was learning.

The closest they came to a serious problem arose during the third week when the Klaxons sounded one night at three A.M., signaling that the oxygen-nitrogen mix was exceeding parameters. Solly didn’t know what to do about that, and the alarms continued sporadically during the next few hours, warning of a deteriorating condition. He growled that for all they knew the problem was with the alarm system rather than life support, but he continued working on it, replacing every part he could reach until finally the clamor stopped.

Kim’s normal high spirits never returned. She no longer wandered through the ship on her own, but rather stayed close to Solly. She read more extensively than ever before, mostly books and articles in her specialty, but also novels and histories and even Simon Westcott, the classic second century philosopher who’d tried to explain how consciousness had developed in a mechanistic universe.

Occasionally, when she was alone, she caught herself speaking to the visitor. “I know you’re there,” she told it, keeping her voice down so Solly wouldn’t overhear.

“Why don’t you show yourself?”