The ‘Tim goes back in time and changes things’ premise (bc yes I’ve been bingeing these lately and I’m in LOVE) but somewhere along the way, Tim gets amnesia.
He doesn’t remember anything about the new timeline he’s created or whatever event led him to go back in time in the first place. So, when Tim returns to his senses after whatever concussion or drug that effected his memories, he just collects his things and goes home.
Against all odds, it actually takes a while for him to realize something’s off. To be fair, he’s very out of it, and very tired in general, and it’s just so easy to explain all the little things not matching up.
Can’t find his keys? Probably lost them on patrol. He can just break into his room.
None of his stuff is there? Curse the brat and his vendetta against Tim’s existence.
None of his passwords work? Guess Bruce is going through another late night paranoia bout and switched them, not like Tim can’t hack in on his own.
The intel board for his latest case is missing? Tim must have moved it around during his own latest bout of late night paranoia.
Alfred staring at him in shock when he runs past and out of the manor? Yeah, he’s surprised he’s up and working without caffeine around this time, too.
It takes a couple of days for Tim to realize something’s changed. A little because he’s still recovering. Somewhat because he’s spiraling into a case. Mostly because he’s avoiding any real interactions with his family (just so that they won’t worry. He’s learned his lessons about hiding multiple injuries. Totally. Definitely. For sure.)
Even so, he finds time to unknowingly terrorize the Bats.
He sees Dick at a coffee shop, grabs his coffee and chugs half of it before running out with a thank you thrown behind him, leaving Dick half bewildered, half indignant and staring mournfully at his cup. He bumps into Jason at the library and they hiss at each other back and forth until Jason actually throws a punch. Tim dodges and laughs, bc it wasn’t anything near the precision and strength Hood usually uses. He says so and then looks at the time and heads out, smiling, leaving Jason utterly disturbed. He snags cookies from Alfred at the manor, earning a double take from the butler so hard that the man has to take aspirin after. He finds Damian in the living room, yells at him for messing with his bedroom, then storms out when Damian just stares at him making short, angry, flustered noises. He sprints past Bruce on his way out. Bruce tries to question him but Tim just waves him off, attributing it to overprotectiveness and seamlessly dodging all Bruce’s attempts to catch him.
Finally, Tim realizes something’s wrong when he gets to his apartment and it’s not his anymore. He uses his trackers to find his suit and it leads him straight to Drake Manor, where he finds Cardinal’s costume, not Red Robin’s. In his confusion he checks his phone for any updates from the family and finds a different date than he expected. A really, really different date.
Dread finally dawning on him, Tim heads over to the cave, taking the motorcycle that’s thankfully still there (albeit a different aesthetic than he remembers). He’s realized that he has amnesia and can’t remember the last… years of his life. Arriving, his panic only worsens as he sees Jason in a non-Hood getup, Batman in an altered suit, and Nightwing and Robin sparring in a very different looking training area.
Suffice to say, everything screeched to a stopped when Tim skidded in on his bike.
After a lot of punching, cursing, and Batarang throwing, Tim finally manages to convince his family that he’s not a super villain. In fact, he tells them the truth he’s at last realized:
He must be in an alternate universe, having taken on the body of their Tim.
Handcuffed to a chair, Tim goes about proving it, giving the assigned code for alt universes and sharing information that only a Batkid and, more importantly, a Wayne would know. Batman finally calls in Zatanna and she analyzes him, telling them she certainly found something alright. Unfortunately, she whispers to Batman and then Tim is forced to sit in the medical bay (still injured), out of earshot, while the rest of his family discuss what she found.
Finally, finally, his family filters into the medbay, all staring at him with wide, unreadable eyes. Then, Batman steps forward and says, “Okay. I believe you.” And crumples a little as Tim lights up like a Christmas tree.
Because Zatanna’s analysis told them it wasn’t alternate universe travel magic covering his signature, but time travel magic. Meaning, all Tim’s proof of familyhood was him remembering being one of them in the alternate time line. Meaning, they had a family member right there all this time who must have known, and yet hadn’t come home.
Meaning, this boy who looked at Batman—at Bruce—with a bright smile and mischievous eyes, who joined his brothers in banter and troublemaking with such ease and familiarity, who was calculating and passionate and sarcastic as everything, was theirs. And they never would have known.
The next few days, Bruce along with Jason, Dick, and Damian conduct their investigations— Cass, Duke, and Steph coming in on it soon after. They pretend they believe Tim, helping him uncover “Other Tim’s” life so they can know more about how he got there, and then help him get home. They ask him questions, playing up curiosities of their “other selves.” Tim fills them all in, chalking up their emotional reactions to shock from learning about such a different alt universe, and asks questions in return.
Bruce becomes more and more heartbroken the more he learns. The more he sees how much Tim obviously loves them. His siblings do too. Anger, grief, and fear run high in Wayne Manor. Batman investigates. Dick gets clingy/distanced in turn. Cass and Steph rotate shifts so their newfound brother is always under surveillance. Duke snoops like he’s never snooped before. Damian and Jason loom in the corners. It’s all they can do not to shake Tim and demand answers he wouldn’t know anyway.
However, as frustration grows, so does their love for their wayward brother and the determination to keep Tim no matter what.
Eventually, after a week or so, Tim wakes up one morning, picks up his cup in the kitchen, takes a sip of coffee surrounded by the chaos of his siblings and grumpy dad, and remembers everything.
Unfortunately, his dropped cup shattering on the floor and his loud, “Oh no. Oh no,” is not subtle in the least, grabbing the attention of the room. Then he’s staring at them in horror as they stare back. Panicked, Tim throws a spare gas bomb, runs up to his room with his family on his heels, and jumps out of his bedroom window.
He makes it a good ways through Gotham, taking a pit stop to throw on a wig, eye contacts, and a different set of clothes. He’s at the docs, about to board a ship when the full power of the Bats comes down on him. Secrets out, his family drags him back to the manor, demanding answers. It’s not long before Tim breaks down.
His plan had been working so well and then he had to go and ruin everything. There was no recovering from this mess up. He’s determined to just ignore them until he can get away again, but his family won’t leave him alone. They pester, provoke, interrogate, and smother him in turn until finally, confronted gently by the real reason he went back in time (Bc there was no way he could have hid that from Cass and the rest of the world’s best detectives for long— body language is their forte), he tells them everything, dog-piled beneath his siblings as Bruce strokes his hair.
Needless to say, he moves back into the manor. There may or may not be a few more attempts to run or self-isolate, but his family knows him now. Maybe not with as many memories as he has (they’re working on that though), but enough to reassure him, for now, that they’re not going to let him go again.