She dug her fingernails into her palms until her eyes watered.

She did everything she could to prolong the baby’s naps, giving it extra formula, drawing the curtains tight. Soon the baby was sleeping nearly 16 hours a day. But always there was the baby monitor.

When she turned it up louder she was certain she could hear things hidden in the noise. It was as if the microphone were amplifying the invisible. Or as if the baby were doing something secret.

She would creep to the nursery and ease the door open, but the baby was always sleeping. And when she went back to her own room, the noises were still there. One night she heard a series of tiny grunts and echoey thumps, as if the baby had climbed out of the crib and was walking around. The baby was only two months old. It couldn’t even sit up yet.

Slowly, she walked down the hall in bare feet. She put her hand on the doorknob and listened. Then she heard it: a creak, creak, creak. She froze. Creak, creak, creak. As if the baby were dangling from the crib rail, the way a toddler might. She pictured the baby dangling and smiling at her.

Taking her hand off the doorknob, she walked back to the bedroom. She got back in bed and lay there, staring at the baby monitor, one red LED pulsing on and off. She turned the volume all the way up. It sounded like an untuned radio. She thought her way into the noise. She heard it: The baby was up. The baby was walking around.

She lay there awake all night. She didn’t go into the baby’s room.

In the morning, with the sun burning in through her curtains, she finally got out of bed. The baby monitor hissed blankly. She turned it off and went into the nursery. The baby was asleep on its stomach, its blanket pushed to one side. She had put the baby to sleep on its back. She hadn’t seen it roll over before.

Stroking the baby’s back, she cooed and baby-talked until it woke. The sweet words made her feel like a liar. The baby came awake in an instant and rolled over onto its back, making her jump. The baby regarded her blankly.

She gave the baby its bottle, then diapered it and dressed it in overalls and a sun hat. She microwaved a cup of yesterday’s coffee and scalded her tongue. She made a piece of toast but left it, buttered and glistening with jam, on the cutting board. She put the baby in the stroller and went outside.

It was a crisp fall morning and she was sweating. She knew she needed help. Mothers weren’t afraid to go check on their babies. And yet the night before she had been absolutely certain the baby had climbed out of its crib.

But whom would she call? And what would she say?

She took the baby to the zoo. It sat alert in its stroller, watching the animals. Almost like another animal.