It started with the sound - soft at first, like the rustling of paper inside the walls of Leah's apartment. She'd only just moved into the aging building downtown, grateful for the rent-controlled unit even if it had peeling paint and a strange smell like mold and something metallic.

The noise always came around 2:13 a.m. She knew the time because she'd begun waking up at exactly that moment, every night, heart pounding, ears straining. The sound came from the air vent above her bed. At first, she thought it was rats. Then, a voice whispered.

"Leah?"

She bolted upright, staring at the vent. Silence. She didn't sleep the rest of the night.

The next day, the superintendent - a hunched man with cloudy eyes named Mr. Rudd - brushed off her complaint. "Old pipes echo. Wind plays tricks."

But Leah wasn't imagining it. The voice came again the next night. Louder.

"Leah. I'm still here."

She screamed, called the police. They checked the place, even opened the vent cover. Empty. No signs of tampering, no one in the crawl spaces. But the officer looked uneasy when she asked if anyone else had lived in the apartment before.

Later, Leah dug through the building's records at the public library. Apartment 4B had been vacant for three years before her. The last tenant, a man named Arthur Clenn, was never evicted. He vanished. No signs of forced entry, no note, no one reported him missing for weeks.

That night, Leah covered the vent with duct tape and a heavy towel. She took sleeping pills. Still, she woke at 2:13. The towel was on the floor. The tape peeled back. And something was moving behind the slats - slow, deliberate.

Not wind.

Not rats.

Two fingers, pale and twitching, slid through the vent.

A voice, raspier now, wet and gurgling, whispered:

"I never left."

The last anyone saw of Leah was Mr. Rudd, knocking on her door three days later to check on the smell. The apartment was empty.

Only the vent cover was open.