“In ‘our’ space-time, as we affectionately call it, the calibrator works perfectly. One puny graviton per photon. But in some dimension five or higher, it spews out a torrent of gravitons.” She leaned back and stared up at the ceiling. “How can I put this in a way you can understand?”

Matt was growing excited. “I think I know what you’re getting at!”

She nodded. “In your primitive terms—they still used string theory?”

“Go on, yes?”

“In that way of thinking, our space-time continuum is a four-dimensional brane floating through a larger ten- or eleven-dimensional universe—”

“Wait,” Martha pleaded, “I don’t understand. A floating brain?”

Matt spelled the word. “It’s short for ‘membrane.’ ”

“They couldn’t just say membrane?”

“ ‘Membrane’ means something else. A brane is like . . . it’s like a reality. Like we live in one four-dimensional reality, but there could be countless others.”

“But where would you put them? Where could they be?”

“They’re inside a larger brane. Five or six or more dimensions. ”

“What would thatlook like?”

He shrugged. “We don’t know. We can only perceive four dimensions.” She nodded slowly, lips pursed.

“All right,” La said. “As Matt said, there are countless other four-dimensional branes, but what’s important are the five-dimensional ones that can be made to envelop ours. Your broken graviton generator attracted one of these beasts and apparently made a permanent connection. Permanent from our point of view. Instantaneous, hardly noticeable, in five dimensions.”

“But in ours,” Matt said, “it makes a closed timelike curve?”

“In a way. But that would only make a time machine that went backward in time. Yours moves forward, faster and faster. Something in that five-dimensional brane is connected to a huge singularity in our brane: the heat death of the universe. The end of time.”

“The End Times,” Martha whispered.

“It’s more than ten to the thousandth power years in the future. The stars die, the black holes evaporate, and finally everything stops moving.”

“I want to go find out whether I can die.” La’s smile was almost a leer. “I think we can help each other.”

16

After tea, they took the machine downstairs, to aroom that functioned as a kind of laboratory. It was austere, evenly lit from glowing walls and ceiling, with a series of identical tables numbered one through ten. Matt, following orders, set the machine on each table for a minute or two while La stared at it without expression. Then she would nod and drift on to the next one.

At the end, she nodded, and then shook her head. “I have to share this with some others. Why don’t you two get some rest?

“You can go anywhere in the place. If you’re lost or want something, just ask for help. Out loud.” She disappeared.

Matt put the machine back into the bag and wouldn’t let Martha carry it. “Look. I’m not a professor here, and you’re not a graduate assistant. We’re just time travelers, both of us unimaginably far from home.”

“But . . .”

“You know the term ‘stranger in a strange land’?”

She nodded. “Exodus 2:22. That’s how Moses described himself.”

“And that’s what we are; that’s the largest thing we have in common. Though the ‘lands’ we came from are also strange to one another, still, this is the one we’re stuck in. Together.”

“I don’t know. I have to think about that, Professor.”

He sighed. “Matthew, or Matt. Please? ‘Professor’ makes me feel old.”

“Only when I say it?”

“Oh . . . maybe. Matthew?”

“I’ll call you Matthew if you let me carry the bag.”

He handed it to her. “Let’s go find a view. It must be close to sunset.”

They walked down the corridor until it ran into a wall, and then followed the wall until it led to an outside door, which opened easily to a parapet that went out about a meter and a half into pure sky—no protective railing.

“It’s gorgeous,” Matt said. The mountains were crimson and orange in the setting sun, with purple shadows deepening to indigo. The shadow of the palace’s pinnacle was a narrow, straight slash.

He stepped out. “Professor! Don’t . . . Matt!” He held a hand out and it hit an invisible, marshmallow-soft wall.

“It’s safe. There’s a pressor field.” To demonstrate, he folded his arms and dropped back against it, which made her gasp.

She put her hands over her eyes. “Please don’t.”

“Okay.” He angled forward and held out a hand to her. “Let’s go find that sunset.” She did take his hand and followed him around the parapet, staying close to the wall.

The sunset was a brilliant wash of color, deep red merging into salmon and an improbable yellow with a breath of green, fading into blue. Inky blue overhead, with a few pale stars.

She stared wide-eyed, her lips slightly parted. Matt noted that her eyes were gray, and she was about as pretty a girl as he had ever stood this close to, even with the small scar. He was still holding her hand.

She let go and touched her sternum. “Sweet Jesus,” she breathed. “My heart is going so fast!”

“Mine, too,” Matt said, though it wasn’t all geology and altitude.

“Maybe . . . we should go in. This is wonderful. But I feel almost like I’m going to faint.”

“The air is a little thin,” he said, sidling around her and taking her hand again. “Go back the same way?”

“Please.” They picked their way around, Matt walking slowly and thinking furiously.

She’s not a young girl, he told himself, in spite of her lack of experience and information. She’s almost as old as Kara was when they broke up a couple of months or millenniums ago.

But you can’t talk yourself out of the truth that she isa child, when it comes to dealing with the opposite sex. Don’t press her; don’t take advantage. Be a man.

Unfortunately, “be a man” was also the counsel the rest of his body was giving.

What if they never did get back to their own times? As they moved on into the future, and people became more and more strange, they would be the only potential partners for one another on the planet.

Her hand was cold and damp. This is plenty of strangeness for the time being. Don’t be a scoundrel. She put her life between you and a crazy cop with a gun. Be a man. Be a man, for a change.

When they went through the door he let go of her hand.

“Thank you.” She leaned against the wall, panting.

“Are you okay?”

“I think so.” She looked up and down the corridor. “You know, she’s right. We should rest. Much as I’d like to explore, I ought to lie down for a little bit.” She pointed. “Is that the way back?”

A valet appeared. “Yes. On your left, second corridor, two doors down.” He faded away.

“I guess they’re always watching,” he said.

“She is. He’s part of her.” She looked around. “That gives me a strange feeling. Like I’m being spied on.”

“I suppose. But she’s been doing it for so long, she’s seen everything.”

“She hasn’t seen medo everything.” She started off down the corridor.

“Wait,” Matt said, and touched the bag’s strap. “Let me take that. You’re tired.”

“All right.” She surrendered it and smiled. “Professor.”

Back in the apartment, she stretched and yawned and relaxed onto the couch. He sat down and set the bag between them.

She looked inside. “Wish we still had that bottle of wine.”

“Yeah,” he said. “The sixty thousand bee shits aren’t doing us any good.” She giggled at that, and there was a knock on the door.

“Come in?” Matt said. The valet eased the door open and entered with a tray. Two bottles of wine, red and white, and two glasses. He set it on the end table next to Martha.

“You did that so fast,” she said.

“No, Martha; La anticipated your requirements. If you had asked for coffee or tea, I would be here with it.”