She was being ridiculous. There was no monster. There had never been a monster. She would prove it to herself.

Maya pulled the floodlight switch by the entry chamber, and light sprung up all around the building. She ran back to the living room, where Tilapia was still asleep. It was out there; she could see it now—or part of it: a snaking body of mercury-colored scales, a blood-red fin all along the top, and no sign of beginning or end.

She couldn't breath. The monster's iridescent scales sent flecks of rainbow flitting around the bunker. It felt like she'd dropped into another world. Her heart was beating so quickly she thought she'd pass out.

She wanted to run to Stepmother, but was stopped by a swath of white in her peripheral. Against her own instincts, she turned to see what it was.

A circle of milky white, maybe four feet across, drifted into view. She could have believed it was the moon fallen into the ocean, but she realized it was the monster's eye, peering back at her. The creature was still, gills fluttering calmly. She was afraid to move.

Mr. Tapia had stopped snoring. She managed to tear her gaze away from the giant eye and saw that the man was now sitting up on the couch, squinting at the reflections dancing around the room. The monster's mouth hung open, revealing transparent, needling teeth longer than Maya's arm.

Tilapia was about to stand when she shouted, "Don't move!" but he was already on his feet. The tides sloshed louder against the outer walls, as if they'd suddenly shifted. The view outside had become a blur of scales as the monster barreled past, circling the bunker.

"What in the—" Tilapia started, but the rest of his words were lost when Stepmother called, "Maya? Where are you?"

She pounded up the stairs.

"Maya, dear, why were you beating on my door?" Stepmother was already dressed and made up. She took Maya by the shoulders and looked her over. "We have to get you out of those clothes. Did you even sleep last night?"

Her clothes were from the day before, now stuck to her with sweat. Her hair and eyes were wild. She grasped Stepmother's arm. "We have to go. We have to get to the submarine."

"Maya," she warned. Stepmother twisted her arm away. "What is this?"

The short silence was enough. The water was alive all around the bunker now, like frisson before a storm. Stepmother lifted her head, brow furrowed.

"Flora!" Mr. Tapia shouted, "Maya! Get to the submarine, n—"

A boom from downstairs drowned his voice. Water rushed against the bunker, giving her vertigo. The alarm blared. The whole building seemed to screech and churn. She grabbed Stepmother's hand and pulled her toward the stairs.

"No!" Stepmother yanked Maya back and wrapped her arms around the girl.

Two impossibly solid doors streamed shut, cutting off the stairwell. She gasped and pressed into Stepmother's body. The doors hissed as they were pressure-sealed. A hatch opened in the ceiling, and a rope ladder whipped down. Stepmother spun Maya to face her and locked her gaze.

"My dear, you have to listen to me," she hurried. "Are you listening?"

Maya nodded. Stepmother didn't wait.

"Get in the escape pod." She pointed to the ladder. "Get to the surface. Set off the signal so they can find you. It's the blue button. Go!"

She pushed Maya forward. There was a loud crack, and then downstairs surged with a deafening roar. Maya clambered up the ladder, unable to hear herself. She didn't look back until she reached the ceiling. Stepmother wasn't behind her; she was still at the base of the ladder, shouting without words and pointing for her to go up.

Maya climbed through a long tube and then onto the seat at the top, strapping herself in like she'd learned in the drills. The roaring subsided, as if downstairs had reached its fill, and all she heard was, "You have to survive."

The hatch closed and Maya was alone.