Did she always whine? Perhaps you just forgot it in the terror of those final moments with her. Or perhaps you’ve further damaged her.
There are techniques in cryptography that allow one party to demonstrate that a given piece of information is true without actually revealing the information to another party. These protocols can be used to verify the authenticity of encryption keys without disclosing the key.
Your perceptions are the result of progressive encryption. The message flows only one direction along the gradient, but you can use knowledge protocols to verify that one piece of information is true for the entire length of the information string.
You can’t retain your memories when you travel back, but you can broadcast one crucial piece of information to yourself. There is only one message that can be transmitted, and it is that this is not the first time the string has been decoded.
You’re watching television with Jane on the couch. Her paws are rough and warm. They smell like Fritos, although you have never eaten Fritos and subsequently found yourself thinking of dog paws. Some information flows only in a single direction.
The claws curve out of the soft fur over her pads. When you take a paw between your palms, she withdraws it, eyeing you for signs of intent to clip her nails. You take her paw again and rest it on your palm, and she watches with liquid brown eyes. Her front leg twitches, prepared to withdraw if the clippers appear.
“We’re holding paws,” you tell her.
There is something satisfying about annoying her just a little, seeing how much stupid behavior she’ll put up with. Sometimes, sitting on the kitchen floor together, you throw your arms around the sable ruff of her neck and hug her. She tolerates it for a moment because it’s you, and she knows you perform many meaningless actions. If someone else attempted this, she would probably bite their ear.
Then you remember, you’re time traveling.
You know nothing more of the future than this simple fact: this is not the first time you’ve lived this moment. At some point in your coming life, you will discover a way to return to this body on the couch with Jane, armed with the alarming piece of information that this is not the first time you’ve been here.
You look around the room. There’s an old episode of a sitcom on TV. Nothing here seems out of place. Why did you pick this moment? You wait, and nothing happens, except Jane rumbles a low growl and withdraws her leg. She stands up and moves further away on the couch. She’s had enough of holding paws.
In a year you put your arm over her and bury your face against her neck. “Don’t leave me,” you whisper, knowing you could never ask this if she could understand. She whines when the needle goes in. You wait for another exasperated sigh, another breath. You put your hands over her soft, warm paws, caressing the rough pads, and she does not pull away.
Did she always growl on the couch when you held her paw?
Did she always lunge at the man?
Did she always whine when the needle went in?
Don’t leave me, you said. But you were the one who left her. She reached the end of her timeline and stopped, while you went on without her. Her life was completely decoded, but you are still living inside the cypher. You should not feel sorry for her.
What would have happened if you’d never loved Jane? You would never have been in the woods the day she showed you she would fight for you. You would never have thought her warm paws smelled like Fritos. You would never have sat together on the kitchen floor, with Jane snuggled against your hip, and realized you weren’t going to get up and make dinner if it meant leaving her.
What would happen if you went all the way back to before you ever met Jane in the shelter? What if the driver of the trash truck went into the shelter before you and walked out tethered to her, and she went home with him, and watched him on the sofa and the kitchen floor, and endured his silly hugs and attempts to hold paws and show his love in all the strange ways you must when you know someone will die but can never speak it?
What would have happened if you were never driving along New York Avenue at 4 a.m. and felt a thud?
You hurt her. If there’s any way to go back and undo the hurt, you’re going to try it.
You go back. You are driving on New York Avenue at 4 a.m. and feel a thud. You don’t see anything in the rearview mirror. A week later you notice the dried blood on the bumper and go to the shelter, afraid of what you will find there.
She deserved better. She deserved never to meet you. You go back again.
You are driving on New York Avenue at 4 a.m. and you are time traveling. You don’t know how you’re aware of this, but at some point in the future you will devise a means of returning to this moment. There is a thud.
Three years later the needle goes in, and you ask her never to leave you.
Jane deserved better than you. You go back.
You are time traveling as you drive on New York Avenue at 4 a.m. There is a thud.
A week later she rears up and breathes in your face in the shelter and looks into your eyes, and you know that you would do anything to save her.
Three years later she is dying, and doesn’t know she’s dying. “Don’t leave me,” you whisper, knowing you can only say it because it’s in a code she cannot understand.
Then you are time traveling and wondering if in every iteration you are harming her further because you can’t let go.
You are time traveling. There is a thud. Again you feel the moment when you wrote the wound on her, inscribed the limp that lasted the rest of her life.
Still you go back.
There’s no way to know how many times you’ve been here. Each iteration feels like the first: a painful crushing-together of unfolded possibilities, the encryption of treasured memories into gibberish. With each reversal of time, the love you felt for Jane diminishes like a failing light until you’re in the shelter the moment before you saw her through the metal cage. Then it winks out entirely. The clocks move forward again, and it bursts into existence, the beginning of a new universe.
Always there is the thud, and always, three years later, the needle. And on this return—the first, or the thousandth—you understand that it’s not your first day that has drawn you back but the last. Not the accident but the needle.
You will go back one final time.
You find a way to fold one additional piece of information into the message you broadcast along the timestring: this is the last decryption.
You don’t go back to undo what you’ve done. You can’t hurt or love her any more than you already have. There’s comfort in that knowledge. You go back, just as you went back after the accident, to find her in the shelter.
You’re time traveling. You don’t know how you know, but at some point in the future you will invent time travel, and you’ve returned to this moment for a reason. But this is the last time.
You are driving on New York Avenue at 4 a.m. and feel a thud.
A week later you find dried blood on the bumper and you go to the shelter. The dogs clamor as you walk by the cages, but none of them are the one you’re looking for. You hear Jane barking as if she is trying to catch someone who is walking away.
This is the last time you will be here. It’s up to you to figure out why.
You stand outside her cage and she rears up to face you.
“Be careful,” says the man from the shelter.
Jane’s flank is shaved over a ragged wound and her front leg is splinted. Her brown eyes are calm and confident. She breathes in your face. You draw nearer.
Jane has been labeled as dangerous. She will need time and training and patience and love. You could fail her. She will never consider alternate timelines or wonder if she deserved better. She will never know when her last day comes.