The note on Aunt Mara’s table is written in the kind of handwriting that does not waste paper.

Storm after dusk. Stay on the boards. If the lights walk, don’t you walk after them. Thermos in the fridge. I am in town getting sandbags. Phone when you can. — A.M.

You are alone in the cottage at the edge of Hollow Marsh, which is a polite way of saying the backyard is a wet, breathing world of alder, peat, and sky-colored water. The power has already blinked once. The wind worries the shutters like a dog with a shoe.

On the table: a field notebook, a stub of pencil, and a lantern with a full battery. Aunt Mara is the marsh’s part-time keeper. She believes in old stories the way she believes in weather radios—useful, incomplete, and not something you ignore.

Out on the marsh, a pale light winks. It does not sit still. It drifts, pauses, drifts, as if someone were carrying a candle over ground that is not ground.

From the alders comes a scream.

It is high. It is wrong. It sounds almost like a person.

You are brave enough to look and old enough to have been told twice not to be foolish. The lantern fits in your hand. The notebook fits in your pocket. The scream happens again, farther left, as if it is moving.

The floating light winks a second time, bluer now, like a thought.