“For someone convinced that she’s meeting a man from a parallel universe,” Jonas deadpans, “you’re rather calm.”

“Do I look calm?” she asks, knowing the answer.

He stands from the chair. “I’m sorry to have unnerved you. Thank you for coming to see me, but I’m afraid Dr. Guyer wasted your time. I have to get out of here.”

He moves for the door, but she stops him. “And go where?”

Jonas turns toward her. Eva stiffens her back. She has no idea why it’s important to her that this person, this apparent miracle, not walk out of her life. She feels a sense of fate. Of destiny. She knows she can’t—shouldn’t, at least—let this man from another world get away. “I don’t need to be a psychologist to know you need help.”

“I don’t have a mental illness,” Jonas assures her.

“I’m not talking about that kind of help. I’m talking about help with . . . with whatever your situation is.”

A bitter chuckle escapes his lips, like ice cracking. “You don’t know what my situation is.”

“Then tell me. Tell me, and I’ll help. Do you believe in destiny, Dr. Cullen?” She watches him ponder the question.

“No. I don’t.”

“Well, maybe you will. Because a psychologist with a working knowledge of physics has just been placed in your path. I don’t believe that’s either accident or coincidence.” Her eyes lock on his. “And I think it’s only a matter of time until you don’t believe it’s accident or coincidence either.”

Eva watches him ponder that. She knows many, many smart people, but she doesn’t think she’s ever met a bona fide genius until now.

“Is there a place to drink around here?” Jonas asks.

Eva’s surprised. “You . . . want to go to a bar?”

He offers up a shrug. “You’re right, I could use some help.” He pauses. “And I bet you could use a drink.”

She takes Jonas to a quiet pub that’s a five-minute walk from the hospital. Every bone in his body croons a chorus of pain from the same broken hymnal, but it’s good to be out in the open air. Even though his stretch in police confinement proved mercifully short, freedom is a cool drink on a scorching day. On the way, she tells him her name: Dr. Eva (pronounced “Ava”) Stamper. She is, he cannot fail to notice, stunning. Almost six feet tall, she wears a tan blouse and a dark gray pencil skirt. The simple outfit complements her ocher skin and striking black hair, which frames her piercing green eyes.

As they walk, Jonas notes that this portion of Switzerland has the same Japanese-influenced architecture he’d witnessed back in France. They pass a newsstand, and he is compelled to stop and examine its offerings, his first exposure to the news of an alternate reality. He doesn’t recognize any of the celebrities on the covers of the glossy magazines. An English newspaper’s headline proclaims, “US PRESIDENT CHANG ISSUES STERN WARNING TO RUSSIA.” The article is accompanied by a photograph of a Chinese man in his sixties whom Jonas doesn’t recognize.

He can sense Eva studying him, taking in his astonishment. She watches as he takes inventory of all the different ways this world is different—and yet not so different—from the one he knows. He expects her to pepper him with questions, but she waits until they’ve both had a chance to get a drink.

The pub is called Pub des Vergers. In English, the name translates to “Bar of Orchids,” which strikes Jonas as a very strange name for a bar. Bottles of beer and liquor stand at attention against a red brick wall, up lit by violet lights. Jonas finds them a table while Eva orders two local beers.

Eva sips hers and laments, “Maybe I should have ordered a stronger drink. Given what I think you’re going to tell me.” She sets her bottle down. “Where should we begin?”

“What do you know about the Many Worlds Theory?” Jonas asks.

“Only what I learned in Introduction to Quantum Mechanics.” She smirks. “Got an A, though.”

“I’ll bet you did,” Jonas says, impressed. A puckish intelligence winks back at him, the same inner glow he first saw in his wife. The warm dazzle he fell so deeply in love with.

He asks Eva for a coin. After digging in her purse, she hands him a two-euro piece. Jonas turns it over in his hands. His intention is to explain multiverse theory to Eva as he did with Amanda. On their first date. The first time their hands touched. The moment comes alive in his memory, and his eyes tingle with the threat of tears.

“Are you all right?” Eva asks.

“Fine,” Jonas croaks, shaking away the memory. He flips the coin, its patina glinting in the light of the pub as it tumbles back into his hand. “Heads or tails?”

“Tails,” she shrugs. Jonas reveals the coin in his palm. Heads. Eva grimaces. “Too bad for me.”

“Not exactly. You see, the Many Worlds Theory holds that there is now a universe—a parallel universe or, if you prefer, an ‘alternate reality’—where the coin came up tails.”

Eva furrows her brow. “That’s never made much sense to me. What you’re describing would lead to an incalculable number of realities. If the universe favors efficiency, it doesn’t make sense that a new one is created every time someone flips a coin.”

“You’re right. The coin flip is just a convenient illustration I use with laypeople.”

She rears back. “Laypeople? You wound me, sir,” she says in mock offense.

“But you happen to be absolutely right,” Jonas continues. “The multiverse does prefer efficiency, which it achieves by limiting branch points—instances where circumstances could go right or left and, therefore, birth a new universe—by constraining the number of times that it happens.”

“How?” she asks.

“By favoring certain outcomes. Which limits the total number of realities in the multiverse from the impossibly infinite to manageably so.”

“And how do you know that?”

He tells her about his Many Worlds Proof. The Nobel Prize. The night in Stockholm. The accident. He doesn’t know how he manages to get it all out and not have his voice tremble.

“I’m so sorry,” she says. There’s more than sincerity in her voice. Jonas senses experience. Eva has trod this unfortunate emotional territory.

“I devised a means to travel between realities,” he says. “My hope is to find one where Amanda is still alive.”

“Your hope? I would think there would be . . . well, I would think there would be a lot. I mean, in a universe of infinite universes.”

“Yes. But you’re forgetting something.”

Eva brightens. “The universe favors . . .”

“Certain outcomes, yes.”

Eva takes a pull from her drink, evidently thinking hard on all that Jonas has unloaded on her. “What happens,” she ventures, “if you find a world where your wife is alive . . . but so are you?”

“I don’t know,” he admits. “I think it’s unlikely, given the universal bias I mentioned.”

“But what if?” she insists.

“Then . . .” Jonas’s voice trails off. “I guess that would fall under the category of a ‘quality problem.’”

“It would certainly make for the world’s most interesting love triangle.”

“Maybe I’ll write a book about it,” he jokes. “Get a Pulitzer to go with my Nobel.”

Eva is still working to absorb all this, wrestling with whether to accept what he’s told her and what she’s observed on his forearm or to hold fast to common sense. “I can’t even begin to fathom the energy expenditure required to jump realities.”