IT WAS THE light that started it. Hannah woke up at three o’clock in the morning one cold February day and noticed that one of the old copper sconces along the wall was turned on, emitting a dim, barely perceptible halo. It flickered at first, then died, then abruptly came back to life again. At first she chalked it up to a faulty wire, or carelessness on her part—had she turned off the lights before bed? But when it happened again the next evening, and again two days later, she began to pay attention.

The fourth time, she was already awake when it happened. She felt around the nightstand for her glasses, put them on, then stared at the glowing bulb and frowned. She definitely remembered turning off the switch before going to bed. She watched as it slowly burned out, leaving the room dark once more. Then she went back to sleep.

Another girl would have been scared, maybe a bit frightened, but this was Hannah’s third winter on Shelter Island and she was used to its “house noises” and assorted eccentricities. In the summer, the back screen door would never stay closed, it would bang over and over with the wind, or when someone walked in and out of the house—her mother’s boyfriend, a neighbor, Hannah’s friends whose parents had houses on the island and spent their summers there. No one ever locked their doors on Shelter Island. There was no crime (unless bike-stealing was considered a crime, and if your bike was gone, most likely someone just borrowed it to pedal down to the local market and you would find it on your front doorstep the next day) and the last murder was recorded sometime in the 1700s.

Hannah was fifteen years old, and her mother was a bartender at The Good Shop, a crunchy, all-organic café, restaurant and bar that was only open three months out of the year, during the high season, when the island was infested (her mother’s word) with cityfolk on vacation. The summer people (also her mother’s words) and their money made living on the island possible for year-rounders like them. During the off-season, in the winter, there were so few people on the island it was akin to living in a ghost town.