The kick came without a warning. Vivian Whitmore’s black shoe struck three-year-old Lily at the edge of the indoor pool, sending the little girl backward into the blue water.

At that same instant, the ceiling lights snapped off. The underwater lamps vanished, leaving one white splash hanging in darkness and the sharp echo of a child’s broken cry.

For a heartbeat, Vivian stood motionless on the marble. Her reflection had disappeared with the light, but her breathing remained steady as Lily struggled somewhere beyond the pool’s silver edge.

“Somebody help me!” Lily cried. Water swallowed the last word, and the sound cut through the enormous room like a door slammed inside a church.

In the east hallway, Ava Whitmore heard the splash. Seventeen years old and wearing worn canvas sneakers, she had been searching for her little sister since dinner ended.

She reached the pool entrance three seconds later. In the faint red glow of the emergency strips, she saw spreading ripples, an empty pool edge, and her stepmother turning away.

“Where’s Lily?” Ava demanded. Vivian offered no answer. She disappeared through the doorway as Ava’s gaze caught a tiny pink sleeve sinking beneath the surface.

Ava did not stop to remove her shoes. She jumped, striking the cold water hard enough to steal her breath, then forced her eyes open against the darkness.

The pool was deeper than she remembered. Her fingers swept past smooth tile, brushed empty water, then found a small wrist moving weakly beneath the surface.

She seized Lily under the arms and pushed upward. When the child’s face broke into the dim red light, Ava held her close and kicked toward the steps.

“I’m here, sweetheart. I’ve got you.” Lily coughed against Ava’s shoulder, her entire body trembling as Ava fought to keep both their heads above the black water.

The steel handrail appeared under Ava’s reaching hand. She pulled Lily toward the shallow steps, placed her on the highest submerged tread, and climbed behind her.

For a terrible moment, Lily only stared. Then a rough cough shook her small chest, followed by a frightened sob that made Ava’s knees nearly buckle with relief.

Ava lifted her sister onto the dry landing. Water ran from her jeans, pooled around her sneakers, and slipped through the grooves between expensive white marble tiles.

The mansion’s pool room was all glass and polished stone, built to impress people who rarely swam. Tonight, its perfect geometry made the dark feel endless.

“Where did she go?” Lily whispered. She was staring at the entrance, where Vivian had stood only seconds earlier, her black dress visible against the hallway lights.

Ava followed her gaze. The hall beyond the glass was brightly lit, but empty. Vivian was gone, and the door was shut tightly against its frame.

Ava gathered Lily in her arms and hurried to the glass door. She twisted the handle. Nothing moved except the loose metal fitting beneath her palm.

She pulled again, harder this time. A dry mechanical click answered from the far side, and a little amber light above the lock blinked once.

Someone had locked them inside from the hallway. Ava had never seen that amber light before, and she knew the door was supposed to open freely in emergencies.

She tested the handle a third time, then stopped. Lily was shivering against her, and anger would not help if the child needed medical attention.

“Look at me, Lily.” Ava crouched to her sister’s height. “You’re with me. Keep talking to me, okay? Tell me about your rabbit.”

“Button has one ear,” Lily murmured through chattering teeth. Her favorite stuffed rabbit was upstairs, probably abandoned on the pink blanket where Ava had last seen it.

“That’s right.” Ava pressed a kiss to Lily’s wet hair. “And Button is waiting for you. We’re going to get back to him.”

Ava knew just enough about water emergencies to be frightened by what she did not know. Lily was coughing and breathing, but she needed a doctor immediately.

Their mother, Grace, had insisted that both daughters learn to swim. She had made Ava practice reaching for the pool wall before she ever let her enter deep water.

Grace had been dead for nearly two years. Ava heard her voice now anyway, calm and practical: First make sure your sister can breathe. Then find help.

At the wall beside the lockers, a red emergency telephone hung behind a clear cover. Ava carried Lily toward it, ignoring the way cold water dragged at her clothes.

She lifted the receiver. There was a burst of static, then silence. She pressed the call button twice, but no voice answered from the security station.