But for some reason, I couldn't talk myself out of it. I was sure it was true. I had lived with this woman for more than twelve years. I knew she was different, and I knew why. I could sense the presence of someone else, an outside person, some intruder in our relationship. I felt it with a conviction that surprised me. I felt it in my bones, like an ache. I had to turn away. …

The baby took the bottle, gurgling happily. In the darkened kitchen, she stared up at my face with that peculiar fixed stare that babies have. It was sort of soothing, watching her. After a while she closed her eyes, and then her mouth went slack. I put her on my shoulder and burped her as I carried her back into her bedroom. Most parents pat their babies too hard, trying to get a burp. It's better to just rub the flat of your hand up their back, and sometimes just along the spine with two fingers. She gave a soft belch, and relaxed.

I set her down in the crib, and I turned out the night-light. Now the only light in the room came from the aquarium, bubbling green-blue in the corner. A plastic diver trudged along the bottom, trailing bubbles.

As I turned to go, I saw Julia silhouetted in the doorway, dark hair backlit. She had been watching me. I couldn't read her expression. She stalked forward. I tensed. She put her arms around me and rested her head on my chest.

"Please forgive me," she said. "I'm a real jerk. You're doing a wonderful job. I'm just jealous, that's all." My shoulder was wet with her tears.

"I understand," I said, holding her. "It's okay."

I waited to see if my body relaxed, but it didn't. I was suspicious and alert. I had a bad feeling about her, and it wasn't going away.

She came out of the shower into the bedroom, toweling her short hair dry. I was sitting on the bed, trying to watch the rest of the game. It occurred to me that she never used to take showers at night. Julia always took a shower in the morning before work. Now, I realized, she often came home and went straight to the shower before coming out to say hello to the kids. My body was still tense. I flicked the TV off. I said, "How was the demo?"

"The what?"

"The demo. Didn't you have a demo today?"

"Oh," she said. "Oh, yes. We did. It went fine, when we finally got it going. The VCs in Germany couldn't stay for all of it because of the time change, but-listen, do you want to see it?"

"What do you mean?"

"I have a dub of it. Want to see it?"

I was surprised. I shrugged. "Okay, sure."

"I'd really like to know what you think, Jack." I detected a patronizing tone. My wife was including me in her work. Making me feel a part of her life. I watched as she opened her briefcase and took out a DVD. She stuck it in the player, and came back to sit with me on the bed.

"What were you demoing?" I said.

"The new medical imaging technology," she said. "It's really slick, if I say so myself." She snuggled up, tucking herself into my shoulder. All very cozy, just like old times. I still felt uneasy, but I put my arm around her.

"By the way," I said, "how come you take showers at night now, instead of in the morning?"

"I don't know," she said. "Do I? I guess I do. It just seems easier, honey. Mornings are so rushed, and I've been getting those conference calls from Europe, they take so much time-okay, here we go," she said, pointing to the screen. I saw black-and-white scramble, and then the image resolved.

The tape showed Julia in a large laboratory that was fitted out like an operating room. A man lay on his back on the gurney, an IV in his arm, an anesthesiologist standing by. Above the table was a round flat metal plate about six feet in diameter, which could be raised and lowered, but was now raised. There were video monitors all around. And in the foreground, peering at a monitor, was Julia. There was a video technician by her side. "This is terrible," she was saying, pointing to the monitor. "What's all the interference?"

"We think it's the air purifiers. They're causing it."

"Well, this is unacceptable."

"Really?"

"Yes, really."

"What do you want us to do?"

"I want you to fix it," Julia said.

"Then we have to boost power, and you have-"

"I don't care," she said. "I can't show the VCs an image of this quality. They've seen better pictures from Mars. Fix it."

Beside me on the bed, Julia said, "I didn't know they recorded all this. This is before the demo. You can fast forward."

I pushed the remote. The picture scrambled. I waited a few seconds, and played it again.

Same scene. Julia still in the foreground. Carol, her assistant, whispering to her.

"Okay, but then what do I tell him?"

"Tell him no."

"But he wants to get started."

"I understand. But the transmission isn't for an hour. Tell him no."

On the bed, Julia said to me, "Mad Dog was our experimental subject. He was very restless. Impatient to get started."

On the screen, the assistant lowered her voice. "I think he's nervous, Julia. I would be, too, with a couple of million of those things crawling around inside my body-"

"It's not a couple of million, and they're not crawling," Julia said. "Anyway, they're his invention."

"Even so."

"Isn't that an anesthesiologist over there?"

"No, just a cardiologist."

"Well, maybe the cardiologist can give him something for his nervousness."

"They already did. An injection."

On the bed beside me, Julia said, "Fast forward, Jack." I did. The picture jumped ahead.

"Okay, here."

I saw Julia standing at the monitor again, with the technician beside her. "That's acceptable," onscreen Julia was saying, pointing to the image. "Not great, but acceptable. Now, show me the STM."

"The what?"

"The STM. The electron microscope. Show me the image from that."

The technician looked confused. "Uh… Nobody told us about any electron microscope."

"For God's sake, read the damn storyboards!"

The technician blinked. "It's on the storyboards?"

"Did you look at the storyboards?"

"I'm sorry, I guess I must have missed it."

"There's no time now to be sorry. Fix it!"

"You don't have to shout."

"Yes I do! I have to shout, because I'm surrounded by idiots!" She waved her hands in the air. "I'm about to go online and talk to eleven billion dollars of venture capital in five countries and show them submicroscopic technology, except I don't have a microscope feed, so they can't see the technology!"

On the bed, Julia said, "I kind of lost it with this guy. It was so frustrating. We had a clock counting down to the satellite time, which was booked and locked. We couldn't change it. We had to make the time, and this guy was a dimbus. But eventually we got it working. Fast forward."

The screen showed a static card, which read:

A Private Demonstration of

Advanced Medical Imaging by

Xymos Technology

Mountain View, CA

World Leader in Molecular Manufacturing Then, on the screen, Julia appeared, standing in front of the gurney and the medical apparatus. She'd brushed her hair and tucked in her blouse.

"Hello to all of you," she said, smiling at the camera. "I'm Julia Forman of Xymos Technology, and we're about to demonstrate a revolutionary medical imaging procedure just developed here. Our subject, Peter Morris, is lying behind me on the table. In a few moments, we're going to look inside his heart and blood vessels with an ease and accuracy never before possible." She began walking around the table, talking as she went.

"Unlike cardiac catheterization, our procedure is one hundred percent safe. And unlike catheterization, we can look everywhere in the body, at every sort of vessel, no matter how large or small. We'll see inside his aorta, the largest artery of the body. But we'll also look inside the alveoli of his lungs, and the tiny capillaries of his fingertips. We can do all this because the camera we put inside his vessels is smaller than a red blood cell. Quite a bit smaller, actually. "Xymos microfabrication technology can now produce these miniaturized cameras, and produce them in quantity-cheaply, quickly. It would take a thousand of them just to make a dot the size of a pencil point. We can fabricate a kilogram of these cameras in an hour. "I'm sure you are all skeptical. We're well aware that nanotechnology has made promises it couldn't deliver. As you know, the problem has been that scientists could design molecular-scale devices, but they couldn't manufacture them. But Xymos has solved that problem."