It is only when she gets home that she realizes she has picked up the wrong package. An ordinary brown paper bag, nothing special. It is only after she opens it that she realizes it is an item that does not belong to her. A retro slender key with a string of letters printed on the handle: OPEN ALL. It is only after she looks through the brown paper bag that she realizes that the name on it is not hers: Elddir. What a strange name. She doesn't even know how to pronounce it.
Maybe it belongs to the previous resident, she thinks. The address on the package is her home, and the house number is the same.
She puts the key together with some letters she has received before and plans to give it to the office. During the first month after moving here, there are letters from previous residents in the mailbox every day. Bank statements. Car insurance. Supermarket advertising. The recipients' names vary, reminding her that the apartment has many previous owners.

The apartment building manager looks up and sees her walking in. She hands the manager a pile of mail while casually glancing past the man in front of her, noticing some packages on the shelf behind him. The name on those packages is also Elddir.
"These are mail for the previous tenant," she says.
"Okay, just give it to me," the manager replies.
The manager opens one of the drawer cabinets. She takes out a key from her pocket.
"This should belong to the previous tenant. I didn't pay much attention and just opened the packages directly."
"The master key."
It is clear that the manager is not really listening to her, as his gaze remains fixed on the key.
"What?" she asks.
"A master key. You didn't know? This key can open all locks."
"All locks?"
The manager's tone is as icy and definitive as a cold knife, severing her train of thought.
"When locks were first invented, locksmiths designed this master key. In reality, the fundamental logic of all locks is the same; it's this key,"
She should question, even argue back. However, the manager simply takes the key, stands up, and opens the door to his office behind him. The door emits a creak as it swings open, jolting her out of her confusion.
The manager hands the key back to her, wearing a smirk with a hint of mockery on his face. She doesn't have time to ponder the depth and tease of that smug smile as she hastily departs.
The key in her pocket feels like a piece of glowing iron. She's burning up, practically on fire. The open door lingers in her mind, and she can hear the creaking sound of the door swinging open as she walks. Too many questions flood her thoughts, and she catches a glimpse of the last light of the setting sun in the sky. She even wonders if she might be able to fly.
She takes out the key and inserts it into the lock of her own front door. There's no resistance; the key goes in smoothly. She enters, closes the door behind her, and changes out of her clothes. It's as if she's following some sort of routine, until she accidentally bumps into a chair by the table, and the sound of the chair's legs scraping against the floor shatters the silence and darkness of the house. It's only then that she realizes she hasn't even turned on the lights.

She opens one lock after another, thoroughly enjoying herself. At first, she could wait until nightfall, taking advantage of the time when people go to sleep to embark on her nocturnal adventures with the key in hand. That key has transformed into a revolving globe, piecing together a brand new map of her fantasies and life. She waves the key, landing randomly in every corner of the city. She begins to relish the dizziness and the excitement of it all. Her once mundane commute becomes her patrol route. Unbeknownst to herself, she starts gazing at doors and locks of various materials with a smile. Glass doors, diaries, safes, jewelry boxes, old and abandoned bookshelves, all conspiring to keep a shared secret with her. Life bestows upon her a new kind of thrill, an uncharted trembling she had never felt before, from the moment she first encounters an unfamiliar lock.

She finally starts to explore her neighbors, and the building that accompanies her day and night becomes her new target and headquarters. She is well aware of her neighbors' routines, which makes it all a bit too effortless. It begins with a beautiful necklace, and she starts taking something from behind every door. In her neighbor's apartment just across from hers, she sees another key. It is just like the one she has, slim and with the inscription “OPEN ALL." The key quietly lies in a weathered ceramic container, alongside the homeowner's wallet, headphones, and a few lollipops. Her heart races, and she feels the heat of her breath. Another fire ignites within her, burning through her body.

There's a scent of burning spreading throughout the apartment building. The fire alarm goes off, and the residents rush out of the building. She follows the crowd, absentmindedly, her hand caressing the key in her pocket. Group by group, people gather in front of the apartment building, waiting for the fire truck to arrive. This moderate fire makes the aging building look even more weathered, with many of its outdated parts and equipment meeting their end. The manager carries a notebook, going door to door, taking notes on what needs repair. She comes to her door, takes out the key, and unlocks it. With a thud, the door lock, with the key in it, falls to the ground, leaving behind a charred, hollow space.