Sarah woke to the familiar creak of her apartment floorboards settling in the night. The clock on her nightstand glowed 3:17 AM, its red digits casting a faint bloody hue across the rumpled sheets. She lay still, eyes wide open, listening to the silence that wasn’t quite silent. There was a hum, low and insistent, like the distant buzz of fluorescent lights in an empty office building. It came from everywhere and nowhere, but mostly, she felt it in her chest.

She shifted, propping herself up on one elbow. The hum persisted, vibrating subtly against her ribs. ‘Just the fridge,’ she told herself, though the kitchen was on the opposite side of the apartment. Sarah was thirty-two, a graphic designer who worked from home, her days filled with deadlines and microwave dinners. Routine kept the loneliness at bay, or so she thought. Lately, though, the nights had grown longer, the shadows thicker.

Rubbing her eyes, she swung her legs over the side of the bed. Her right foot tingled, as if it had fallen asleep, but she hadn’t been lying on it. She flexed her toes experimentally, watching them curl and uncurl under the dim light. Normal. The tingling faded, replaced by a faint itch beneath the skin, like a whisper of movement. She scratched at her ankle absentmindedly, nails digging into flesh that felt… foreign.

By morning, the incident was forgotten amid coffee and emails. But as she sat at her desk, sketching logos for a client’s rebrand, her left hand twitched. Not a spasm, exactly—more like it hesitated before following her command to click the mouse. She paused, staring at her fingers splayed on the pad. They looked the same: pale, with bitten nails from nervous habits. She wiggled them. Fine.

The day dragged on. During lunch, while chopping vegetables, the knife slipped—not from clumsiness, but because her hand seemed to pull back at the last second, nicking her thumb instead of the carrot. Blood welled up, bright and accusing. Sarah sucked on the cut, heart pounding irrationally. ‘Clumsy,’ she muttered, bandaging it. But deep down, unease stirred, a cold tendril uncoiling in her gut.

That evening, as rain pattered against the window, the hum returned. Louder now, rhythmic, like a heartbeat not synced with her own. She turned off the TV, muted her phone, but it persisted, originating from inside her skull. Lying on the couch, she pressed her palms to her ears. Useless. Then, faintly, beneath the hum, a word: *Mine.*

Sarah bolted upright, breath catching. Imagination, stress. She’d been single for two years, buried in work since the breakup. Her therapist had warned about anxiety manifesting physically. But *mine* echoed, soft and insistent, from the hollows of her chest.

Sleep evaded her. At 2 AM, she paced the living room, shadows dancing like specters. Her reflection in the darkened window caught her eye—pale face, dark circles. She leaned closer, and for a split second, her reflection’s eyes blinked out of sync. She jerked back, pulse racing. Trick of the light.

The next day, she called in sick. Googling ‘body twitches anxiety’ yielded forums full of similar stories—nothing sinister. Still, she booked a doctor’s appointment. Dr. Patel was brisk, efficient. Neurological exam normal, bloodwork ordered. ‘Likely stress,’ he said. ‘Try meditation apps.’

But the incidents multiplied. While showering, her arm lifted without volition, tracing symbols on the fogged mirror—curved lines, archaic-looking. She gasped, scrubbing them away, water scalding her skin. At her desk, her fingers typed gibberish into an email draft: *Not yours stop fighting let go.* She deleted it frantically, cheeks burning.

Nights became torment. The voice grew clearer, a sibilant whisper weaving through her thoughts. *This body. Mine. You are the guest.* Sarah plugged in earbuds, blasting podcasts, but the words slithered past, intimate as a lover’s breath. She stopped eating, afraid her hand might disobey and plunge the fork into her throat. Mirrors were avoided; glimpses showed her eyes darkening, pupils dilating unnaturally.

Friends noticed. ‘You look like hell,’ said Lisa over video call. ‘Come stay with me.’ Sarah declined, paranoia blooming. What if it followed? What if *it* spoke through her?

She researched obsessively: parasites, dissociative identity disorder, brain tumors. Nothing fit. One forum thread chilled her—users describing ‘internal watchers,’ dismissed as schizophrenia. But Sarah wasn’t crazy. She double-checked locks, drew curtains, isolated herself in the dim glow of her laptop.

A week in, the pain started. Sharp stabs in her abdomen, as if something clawed from within. She curled on the floor, sweating, whispering prayers she half-remembered from childhood. The voice laughed, a wet, gurgling sound. *Fight all you want. I’m waking.*

Desperate, she drove to the ER at midnight. Scans, IVs, questions. ‘Gastroenteritis,’ they said, prescribing anti-nausea meds. Discharged by dawn, she clutched the bottle like a talisman.

Home, alone again, the whispers crescendoed into murmurs, then sentences. *Sarah isn’t real. I am Sarah. You stole me.* Memories flickered—not hers? A childhood accident, falling into a river, cold water filling lungs. No, that was hers. Wasn’t it?

She smashed the bathroom mirror, shards glittering like teeth. Blood trickled from her palm, but the pain was distant, muffled. Her reflection in a shard grinned back, teeth too sharp.

By the tenth day, movement betrayed her constantly. Legs buckled mid-step, sending her crashing into furniture. Her jaw clenched against her will, forcing out words: ‘Help me.’ But her voice—raspy, not hers.

She armed herself: duct tape binding wrists to prevent self-harm, sedatives hoarded from the prescription. Taped to her bed, she waited for dawn, tears streaming. The voice soothed now, mockingly tender. *Soon. Let go.*

Hallucinations bled into reality. Shadows writhed on walls, forming faces—her mother’s, accusing; her ex’s, laughing. The hum was a roar, drowning thought.

In the pre-dawn hush, clarity pierced the fog. A memory surfaced, unbidden, vivid: not a fall into a river, but pushing someone—a girl, her reflection? No. Younger Sarah, standing by a crib, whispering to a doll. Wrong.

The bindings loosened somehow—her fingers working free with alien dexterity. She stumbled to the desk, opened her laptop. Old photos: childhood albums digitized. There, age ten: two girls, identical twins. Caption: ‘Sarah and Emily, inseparable.’

Twins? She had no sister. Parents died in a car crash; only child. But the photo persisted, real. Digging deeper, emails from a forgotten account: ‘Emily’s episodes worsening. Doctors say absorbed twin syndrome? Vanishing twin.’

The voice purred. *Yes. I vanished. But not gone.*

Panic surged. Absorbed twin—fetus reabsorbed, rare, usually harmless. But this…

Her body seized, convulsing. She collapsed, vision tunneling. Inside, pressure built, a birth in reverse. Skin stretched, bones shifted with wet cracks.

When awareness returned, she wasn’t alone. In her mind, two presences warred. *My body,* the other snarled. *I waited years, growing in silence, feeding on your life.*

Sarah fought, clawing mentally at the intruder. Flashes: her life, stolen moments. The river—Emily’s drowning attempt? No. Emily had been the weak one, absorbed early, but her essence lingered, mutated, waiting.

The twist uncoiled fully: Sarah wasn’t the original. *She* was Emily, the survivor, but the absorbed twin’s consciousness had lain dormant, mimicking, until now awakening fully. All those years, the ‘normal’ twitches, the forgotten dreams—warnings ignored. The body was rebelling against the imposter Sarah, the one who’d claimed it.

No: deeper. The voice confessed in glee: *You are me. I am the body. You are the parasite, slipped in during gestation, controlling the shell. I, the true Sarah, am rising.*

Doubt shattered certainty. Childhood memories fractured—hers or borrowed? The photo showed two, but only one lived. She’d been the shadow, puppeteering the flesh, convincing herself she was real.

Her limbs tore free, not by her will. Hands—*its* hands—clawed at throat, nails rending skin. Gurgles escaped: ‘Out… now.’

Vision faded to black, but sensation lingered: expulsion, a slimy uncoiling from nerves, sliding into void. Last thought: *Not mine. Never was.*

The body rose, blinked clear eyes. True Sarah smiled at the mirror, whole at last. Outside, rain fell, washing away the night’s horrors. But in the trash, amid bloody bandages, something twitched faintly—ejected, writhing, hungry for a new host.