Other Jonas applauds and points to another corner of the wall, jabbing his finger in the direction of more equations. “And to risk butchering this analogy, you’re going to want to be very specific about the type of electricity you use for the top-off.”

Jonas turns to the equations, the theoretical physics memorialized there. “You’re saying I need to recalibrate what remains of the quantum energy in my cells with radiation of the correct wavelength to send me to the reality where Amanda is.”

“The last time you reality-slip, yes,” Other Jonas confirms. “But I think my battery analogy is more elegant.” He swats the idea away. “Point is, you need a battery charger in the form of a particle collider.”

Jonas points back to the baseboard with Other Jonas’s formula for the third universe. “And to calibrate the collider based on those calculations.”

“He finally gets it,” Other Jonas notes, fatigued.

“Not entirely. Why can’t I just save myself a reality-slip? Why not just use a particle collider in this universe?”

Other Jonas gives a chuckle that sounds like radio static. He works his way over to a section of the wall where a newspaper article is taped. He takes it down and hands it to Jonas.

Jonas scans the article. Another gut punch. “They shut down CERN,” he gasps. “What about—”

“Other accelerators? Keep reading.”

Jonas does. In this universe, the Large Hadron Collider was the last particle collider to be decommissioned. In this universe, an accident at New York’s Brookhaven National Laboratory killed thousands, leading to global protests—most fueled by the religious notion that smashing protons together was the exclusive province of the divine—which ultimately resulted in shutting down the world’s thirty thousand particle colliders.

“That’s madness,” Jonas hisses.

“What, there are no moral panics in the universe where you come from?” Other Jonas cannot keep the disgust from his voice. “This universe positively exults in them. The point is, you have two choices: break into one of the decommissioned accelerators and try to start it back up—which, having tried it, I really wouldn’t recommend—or reality-slip again and hope for a more scientifically tolerant universe.”

Hope. Jonas’s thoughts lurch once again in its direction. With renewed urgency, he snatches the paper and pen from his counterpart’s hands and returns to the baseboard, scribbling formulae with a fury. Anticipation wells up within him with each stroke. Perhaps his doppelgänger’s mania is contagious.

As Jonas writes, he hears Other Jonas cautioning, “All that being said . . . and I say this knowing what you promised yourself—what we promised ourselves—you should consider the fact that the energy dissipation, the ticking clock, the fact that every collider has been mothballed in this reality . . .”

“Means what?”

“That you can’t swim against the tide of the universe.”

The pen nearly breaks under Jonas’s hand. Once again he feels the sensation of someone stepping on his grave. “What?”

“I said, ‘You can’t swim against the tide of the universe.’”

“I knew a woman who said that exact same thing to me once.”

“Eva Stamper.” Jonas reacts, surprised to hear that name. “I guess we’ve both met her in our travels,” Other Jonas muses. “Interesting.”

“‘The universe favors certain outcomes.’”

Now it’s Other Jonas who regards his twin with pity. “Reality-slip yourself home,” he implores. “Before the quantum energy leaves your body forever. And if you can’t find home, find somewhere livable, and do what I never could.”

“And what’s that?”

“Move on.”

Jonas shakes his head. His other self may as well have suggested that he learn to fly. “You know us both better than that.”

Other Jonas, his face full of condolence, pads over to the nightstand and places a reverent hand on the stack of papers chronicling the slow destruction of Jonas Prime’s life. “The only thing I know anymore is what we do once hope is lost.”

“That’s why I don’t lose hope,” Jonas says. His voice is iron. He folds the paper and slips it into his pocket. The sensation of it against his leg brings comfort. “I’m sorry I can’t stay to—” He searches for the right words. “To help you.”

With that, he turns away. It’s hard to leave him in this squalor, flirting with madness, a dead body rotting away beneath his feet. But Jonas doesn’t have a choice. His crusade requires complete devotion. He’s almost out the door when he feels Other Jonas’s grip on his shoulder.

“And what do you do if you can’t find Amanda? What do you do when the effect wears off and you’re trapped in a reality without her?”

“Then I kill myself and be with her that way.” But both men know that’s not how true love works. That Jonas is giving voice to his grief, not his soul, which knows better, which knows he needs help. That part of him—crying for aid—slips from his counterpart’s grip and out of the apartment. He hears the door close behind him and wills himself forward with the same admonishment he’s repeated countless times over the past two years.

Don’t look back.

NOW

Only in the mind of a scientist, Victor reflects, could curiosity eclipse vengeance. The thought of sabotaging Jonas’s tether remains warm, a comfort. But he set it aside once the Cray reported that Jonas had returned to his Riverside Drive apartment. By his count, that would make at least three separate universes where Jonas had chosen to call the brownstone home.

Victor had been so singularly focused on revenge that he hadn’t taken the time to consider a multiverse’s worth of Jonases. He knew they existed, of course. But his hatred for “his” Jonas was so lasered that the notion of doppelgängers was an unwelcome distraction. Now, though, the thought of Jonas finding a twin—meeting him, talking to him, and, God forbid, gaining assistance from him—can’t be ignored.

And so Victor stands in a living room, which stirs a memory of visits he’d made to the same home in another universe. But now the place reeks and is in disarray. He finds an arrangement of photographs, all turned down or backward. The Jonas who resides in this universe knew Amanda and lost her. The thought brings a smile.

He stands there for longer than he should. At some point, Jonas—this universe’s version or the one Victor knows—will either come home or hear him walking about. Victor should be concerned, afraid of a confrontation, but he isn’t. That’s what the M&P 9 Shield at the small of his back is for.

A voice comes from the apartment’s recesses, slurred and laced with humor, but the voice is unmistakably Jonas’s. “Came back, huh? Nice to see you come to your senses.” An amused snort. “Always knew I was smart.”

Victor follows the familiar voice and enters the bedroom. The smell is significantly worse in here. Black garbage bags hang over the windows. The only furniture is a ladder, a chair, the bed, and a nightstand burdened with stacks of papers. The once-white bedsheets are a grayish yellow and swirled in a torrent. Equations, sketchy and desperate, flow across every wall. Erratic though they might be, Victor sees in them the calculations of multiversal destinations.

And then he sees him. Standing near the bed. Bloodshot eyes. Sallow skin painted with a thin layer of stubble. A mop of hair as unruly as those bedsheets. But still recognizable as Jonas. At least, a Jonas. He sways on his feet. A bottle of bourbon, with maybe a mouthful left in it, dangles from his fingers.

“Who the hell are you?” this Other Jonas says, his tongue languid. Whatever fear he might have of an intruder in his home has evidently been muted by the bourbon.

Interesting, Victor observes, apparently I don’t exist here.

He returns his gaze to the equations on the wall. That this universe’s Jonas managed to develop the Many Worlds Proof without a Victor Kovacevic to crib from should be vexing. But Victor’s narcissism stands against the thought like a wall, preventing him from entertaining the notion that any version of Jonas is capable of discovering the secrets of the multiverse without drafting off Victor’s brilliance.

“Who are you?” this Jonas barks, louder and more insistent than before.

Ignoring him, Victor continues to study the manic formulae carpeting the walls. He pushes through the scattershot mania of the equations, working to excavate the math, the thinking, that lies beneath.

“Hey!” Other Jonas is shouting now. “Get the hell out of here before I—”

“Before you what?” Victor cuts him off. “You can barely stand up, Jonas.”

“How do you know my name?”

Victor waves at the walls. “Where did you get these calculations? Are they yours?” His voice adopts the tone of accusation. “Are they his?”

“Okay, that’s it. I’m calling the police,” Other Jonas threatens, despite the dead body beneath the closet. He begins to hunt for his phone, but the search appears hampered by his inebriated state. Victor slams him up against one of the annotated walls.

“Where,” Victor repeats, his voice clipped with impatience, “did you get these calculations?”