"All of us?" Sasha looked at Neil, at Arthur, and then at Mike. "How can you be sure?"

"Because you've all been through the Door," Mike said. "Just like Olaf said, anyone who's gone through would have switched."

"This is nonsense," said Olaf, and for a brief moment he sounded like Bogart, too. "We were all given multiple exams."

"The exams were all looking for something that had gone wrong," said Mike. "Nothing else. And they still missed something important, something you wouldn't've thought to test for."

"What?" Jamie's eyes were calm, but still wide.

"Disease," Mike said. "Each of you is carrying different versions of the flu, the common cold, and probably some other stuff that never took hold. And you've all got different resistances. That's why there've been so many sick days." He shrugged. "I'm tempted to say that's what caused the last two or three flu scares here in San Diego."

Olaf brushed the words out of the air. "The many worlds interpretation is nonsense," he said. "It's a mathematical party trick, nothing else."

"We would've noticed," said Neil. "How could someone be replaced without everyone else noticing?"

"You did notice," Mike said. "All of you did. You just didn't understand what you were seeing."

Arthur furrowed his brow.

"When I first came out here," said Mike, "most of you mentioned memory problems. Arthur, you told me you'd forgotten the date of your anniversary. Bob was confused about which trailers Jamie and Sasha lived in. Olaf thought his office was on the other side of the hall."

"My office is on the other side of the hall," snapped Olaf. "It was another one of Bob's stupid jokes."

"We've been busy," Jamie told Mike. "Forgetting things isn't that surprising."

"Except none of you actually forgot anything, did you?" He looked at each of them. "None of you ever drew a blank, you all just remembered something different. Something from your native reality."

"I don't remember anything different," Sasha said.

"Neither do I," said Jamie.

"It wouldn't be different to you because it would line up with your experiences. But those experiences don't always line up with the facts here." He looked at Jamie. "When we were at the bar, you told me you had a cat named Spock growing up."

She shook her head. "No, I told you, my cat's name was Isis."

"Your cat was named Isis," said Mike, "but I remember Spock because you aren't the Jamie I was talking to in the bar."

"You were right next to me."

"Not me," he said. "Another me on another world. The experiences don't line up." He glanced at each of them in turn.

Sasha looked around the room. "So this is the mirror universe?"

Mike nodded. "From your point of view, yeah."

"But you're not all evil?"

He shrugged. "No more than usual, I guess? I don't know what you think we're supposed to be like."

Neil looked at his hands. "You're saying I'm from another dimension? I'm not from here."

"If it makes a difference," said Mike, "the Neil you replaced wasn't from here either. According to the reports, Neil made his first crosswalk last January. He's been gone ever since."

"Not necessarily," said Arthur. "There's a chance the native Neil could've been shifted back the same way this one was."

Mike shook his head. "You're talking about millions of potential realities. Billions. The odds of finding the same one again are astronomical."

"How can you know it's not the same one every time?"

"Because you're not all like Bob. If you were all from the same place, you'd all be from there. And you're not."

Neil was still studying his hands. His wedding ring. "So my wife...the woman I've been sleeping with for the past year and a half...isn't my wife?"

"Sort of," said Mike. "She's the same person. You probably still have a lot of the same experiences together."

"But she's not my wife," said Neil. "She's not the woman I married. She married some other me."

Mike didn't say anything.

Arthur's eyes went wide. "Ben Miles."

Mike nodded. "He didn't have a breakdown. He doesn't remember his wife because the Ben who came out of the Door married someone else. His wife really is a stranger to him. An impostor."

"They locked him up for nothing."

"I'll talk to Reggie in the morning," said Mike. "We'll get him out."

"Oh, Jesus," said Neil. "I've been cheating on my wife."

"You've been cheating on her with her," said Sasha. She rubbed her chin. "It's not that bad."

"Yes it is."

She looked Mike up and down. "You're not the guy I was flirting with back in Washington?"

"Definitely not," he said.

She turned to Arthur. "And you're not the man who recruited me at DEF CON?"

He shifted his feet. "Apparently not, although I remember recruiting you there."

"It doesn't seem to make that much of a difference," Sasha pointed out. "I mean, we've all been functioning fine. It's been six weeks since my last crosswalk, and I haven't had any problems. None I've noticed, anyway."

Neil grabbed a handful of hair above his ear. "How can you all be so calm about this?"

"It would stand to reason," mused Arthur, "that with the number of potential realities, there would be an almost infinite amount with negligible differences. We step through the Door and there's a small change. Something that either slips by or we brush off as a minor mistake of some sort. The date of an anniversary. The name of a cat." He glanced at Olaf. "What side of the hall your office is on."

Olaf didn't say anything. His stare was focused just past Jamie's shoulder. Mike wasn't sure if he was trying to keep an angry outburst in check or if he was deep in thought.

"Eventually, though," said Mike, "you'd end up with an undeniable difference. Someone comes through from a more divergent reality."

"Someone like Bob," said Jamie. "Or Miles. Or me."

"You're not quite as extreme a case as Bob," said Mike, "but, yeah." He considered taking her hand, but decided he shouldn't. Under the circ.u.mstances, with all she was getting hit with, it needed to be her choice.

"And would we have even known about Jamie if..." Arthur looked at the table. "Forgive me for being blunt, but it seems you two are sleeping together, at least."

"Neither of us slept," Jamie said. She managed a half-smile. "And I thought he was somebody else at the time."

Mike's cheeks warmed. He tried to tighten his lips and push past it. Sasha chuckled.

"My point is," continued Arthur, "there may be several differences that just haven't come up for the rest of us because there's nothing to put them in context. How long would your lack of scars have gone unnoticed if, well, someone hadn't seen you...naked." He looked down at the table again on the last word.

"I'm sure I would've worn something revealing sooner or later."

"You've been happier," said Neil. "I just figured you were so relieved that nothing went wrong when you crosswalked."

Sasha nodded. "It's been a little weird. I just figured..." She glanced at Mike and smiled. "Well, I figured you two slept together that first night."

Jamie raised an eyebrow. "Are you saying you thought I just really needed to get laid?"

Now they all chuckled. Even Neil made a tight grin.

"I'd guess," said Mike, "this might be one of the reasons you've all been tense. Everyone's body language is wrong. Each time someone went through the Door, he or she ended up surrounded by people whose movements and gestures all felt off. And he or she would seem wrong to everyone else. Just little things, on a subliminal level." He looked at Arthur. "You told me that half the time you felt like you were surrounded by strangers. In a way, you were right."

They all looked at one another. Studied one another.

Mike took another breath. "And I figured out something else, too."

Neil sighed. "More bad news."

Mike crossed his arms, stared at Arthur, and counted to five. "None of you actually know how the Door works, do you?"

Arthur took in a breath and raised his hand. Now that Mike was looking for them, he could see the way all the facial muscles shifted in time with the movement, how the lips formed words that came quick but with no urgency. It was a practiced motion, something prepared and rehea.r.s.ed.

Then someone cut him off.

"No," said Olaf. "No, we don't."

THIRTY-FIVE.

"Olaf, you've signed a number of-"

"Give it up, Arthur," he said. "It's over."

"We all agreed-"

"It's over," Olaf said again. "He figured us out."

Arthur made a point of not looking at Mike. "You and I both agreed that we wouldn't-"

"You and I didn't agree to anything," said Olaf. He waved his hand at Mike. "He's probably right and I'm not the guy who discussed anything with you."

"But you know what we discussed."

"f.u.c.k it," said Sasha. "Olaf's right."

They all traded glances for a few moments. Neil played with his wedding ring. Jamie squeezed Mike's hand, then let go and settled back into her chair.

Another moment of silence pa.s.sed.

"So," said Mike, "should I keep making educated guesses, or does someone want to explain how you built this thing?"

More looks went between them. Then Olaf cleared his throat. "The SETH project was a disaster," he said. "On every possible level. We'd been kidding ourselves for ages, and then we were just in deep denial, even after the failure with the first two test blocks. After Tramp, we knew it was all downhill. Especially for me and Arthur. No more grants, no more research. For the rest of our careers, we were going to be the idiots who killed a dog trying to teleport it. If we were lucky, we'd end up teaching Physics 101 at some community college."

Olaf paused to rub the bridge of his nose. "I came up with the idea of the Door as a way to stall the inevitable. We thought we might get an extra year or two before anyone realized we weren't producing anything. Enough to maybe dim the memory of SETH a bit."

Arthur coughed into his hand. "There is some real science behind the Door," he said. "It wasn't a complete hoax. It was just decades, maybe centuries past what we actually knew how to do."

"It was like NASA's warp drive project," said Sasha. "It's hypothetically possible, we just don't know how to make it work in practice."

"But it does work," said Mike. "How'd you do it?"

Arthur and Olaf glanced at each other.

"Well?"

"We got drunk," said Olaf.

"Beg your pardon?"

Arthur pulled off his gla.s.ses. He reached for a tie he wasn't wearing, sighed, and polished them on his shirt sleeve. "We managed to hold off Magnus for fourteen months," he said. "And then he demanded to see something. Some sc.r.a.p of proof that we were making progress. If not, he wasn't going to renew our funding. And we had nothing. We'd constructed the rings, the whole system, but without the equations to make it all work it was just a very powerful, very expensive electromagnet. We'd hit the end of our careers.

"Olaf came to my office, and we each had a double whiskey. Then another one. And a third."

"Then we sent someone out to get more," said Olaf.

"Me," Jamie said.

"Was it you? I don't even remember anymore."