on a random day in metropolis, superman gets hit with an amnesia spell. at first he thinks it's a dud—nothing happens, and he can't exactly ask the sorcerer what was supposed to happen, so he wraps up the fight and flies home, changing out of the suit and returning to life as clark kent.
clark kent wakes the next morning with no recollection of the event. unbeknownst to him, he forgets every aspect of his life that's remotely related to his being an alien. forgets getting his powers, forgets learning how to use them/control himself, forgets the spaceship hidden on his parents farm, forgets saving people all across metropolis and the world, etc. etc.
but then he starts experiencing these...oddities. like that morning, when he reached for his coffee while reading an absolutely horrific article about luthor that was pure propaganda—and he crushed his mug in his hand. at first he thought maybe the mug had been cracked and he didn't know. but the steaming coffee hadn't burned his hand, and the jagged ceramic edges hadn't cut him, either. or on his way to work, when he realized he was running late, and he cleared the distance between his apartment and the daily planet in half the time it normally took him. or the way his vision had gone telescopic when he squinted his eyes to see something far away. or when he accidentally vaporized the bag of popcorn in his microwave before he even closed the door.
all of this happens, and clark thinks, honest to god, that the only explanation is that he and superman switched powers.
which is to say that he somehow has superman's powers and now superman is somewhere out there with none. which must be why he hasn't been spotted for over a week, now.
because clark accidentally stole his powers.
clark panics. but doing so only results in a splintered coffee table and a scorch mark on his bathroom tile. he folds in on himself on the floor in the middle of his kitchen, squeezing his eyes shut and forcing himself not to touch anything.
he gets a call from his ma. clark has no idea how she has such impeccable timing. with a shaking hand, he applies the barest pressure to his phone and answers the call. ma asks if he's okay, says she hasn't heard from him in a while. she wants him to drop by the farm soon. clark can't tell her about the power he's somehow gained, but he lets her reassure him and promises to make the trip to her soon.
comforted by ma's words, clark goes to the closest place he knows with someone he can (hopefully) trust: gotham.
batman and superman have been featured in the paper multiple times together, mostly concerning their joint work in organized crime busts. clark has reason to believe they're at the very least some kind of coworker, maybe even friends. batman will be able to help clark track down the real superman and return his powers. batman will be able to help clark control his infernal abilities and eventually get back to normal.
he manages to get into gotham without any more incidents, but getting batman's attention is a different story. he could flick on the batsignal...but it's reportedly on the GCPD roof and clark really doesn't feel like trespassing on that specific property. he eventually succeeds by accident, when he gets cornered in an alley at knifepoint with the attacker demanding his wallet.
batman swoops down, silent as a shadow. he dispatches the attacker and unholsters his grappling gun to leave, but clark shoots forward with too much speed and crashes into him. they land in a heap that quickly turns into clark pressed firmly into the ground with a batarang to his neck and his wrists held in a firm grip by batman's other hand.
"wait! please, i didn't mean to do that. something's wrong with me," he says emphatically, cursing the wetness in his eyes. even now in the small alley, the sheer amount of noise clark can hear is overwhelming. he knows how crazy he must look—entirely disheveled, hair unkempt, eyes wide and half-crazed with desperation. he just needs to say something that will make batman believe him. "it has to do with superman."
that gives batman pause. clark leaps at the opportunity.
"this is going to sound crazy, but i think—i think that magic guy he fought a couple weeks ago took away his powers and gave them to me."
batman stares at him blankly. "what."
"i don't know," clark stresses. "here, look—" he pulls one of his hands out of batman's grip easily, wrapping it around the batarang tightly—how does he know the name for this thing?—and when he opens his palm, the metal has crumpled and his skin is unmarred. "see? i woke up with these stupid powers and now i can hear everything and see everything and it sucks—"
batman pulls away from him and stands, his cape enveloping him whole. clark scrambles upright, wringing his hands anxiously.
"...i believe you," batman says eventually. he glances down at the crumpled batarang with a curl in his lip.
clark's shoulders rise to his ears, face tinting pink. "sorry."
batman takes him to a safehouse. he sets clark up with food and clothes and even brings over a red sun lamp that actually helps, to both of their surprise. both of them hunker down and try to track superman's movements. they spend days together in the safehouse searching for clues and trying to hone clark's newfound powers.
clark tries his hardest not to develop a crush. but batman is so gentle and accommodating with his powers, and he brings clark thai food after learning it's his favourite, and he cracks wry jokes out of nowhere that have clark barking out a surprised laugh. needless to say, clark never stood a chance.
he keeps it to himself. there's absolutely no way batman, of all people, would reciprocate his feelings. and he'll probably never see him again when this is all over.
they find the sorcerer. well, batman does. clark watches from a monitor connected to the cowl's camera as batman confronts the magic user and demands that he reverse the spell. after some less-than-gentle persuasion, the sorcerer agrees and clark gets swallowed by a burst of light.
he wakes on the floor with batman hovering over him, concern etched into the line of his mouth.
"did it work?" batman asks, helping clark to sit.
clark looks around the room. he hears someone laugh a city away. he also remembers tearing around the living room as a kid and destroying a side table after tripping over his shoe and faceplanting right into the wood. he focuses his vision and sees the moon through six floor of the apartment building. he remembers pulling batman out of a house fire last month and sticking by him until he was sure everything was fine. he listens to batman's steady heartbeat. he remembers his own spiking when batman smiled at him for the first time after a gruelling mission.
clark can only shake his head in disbelief. he doesn't see a way out of this without compromising his identity. and he only has himself to blame. how embarrassingly predictable of him to run straight to batman and fall for him again.
batman sighs harshly next to him, misunderstanding. "the sorcerer is still in custody. i'll go question him again."
"no," clark reaches for him, grasps his wrist. "it worked. he reversed the spell. just not the way we thought."
batman peers at him carefully, his squinted eyes darting between clark's. after a long moment, his shoulders drop and his jaw firms.
"...you're superman, aren't you."
clark's shoulders hunch. "i'm so sorry, i had no idea—"
he's cut off by batman's laugh.
clark watches in disbelief as batman's mouth stretches in a wide smile and he doubles over, pressing his forehead to clark's shoulder and absolutely cackling against him.
"no, stop," clark says, pushing at him weakly with his own budding smile. "this is not funny. do you have any idea how stressed i was?"
that only makes batman laugh harder. he grips at clark's shoulders and hangs his head, his smile never dimming.
it's contagious. through his own laughter, clark says, "i can't believe myself."
and batman just shakes his head and says, "i can," and kisses him.