The Fresnel lens is a stack of glass stairs in a circle. Each ring is a little prism. Together they bend light the way a giant lens would, without the giant weight. Even dead, it is greedy. It catches the cottage window. It catches a streetlamp in town, tiny as a seed. It catches something on the water and throws it at your eye as if the throw were a conversation.

You move left. The “answering ship” moves. You move right. It moves. That is not a crew with manners. That is geometry.

When the fog thins for a breath, you see the cheat: a buoy with a small real lamp, and behind it, doubled, a smear of town light sitting on the cold layer of air. Tess has a word for the doubling, from Mr. Peck’s folder: looming. Light bending because cold water makes a lens of the air. Folklore called it a ghost ship. The ghost is weather wearing glass.

Your heart is still a drum. Knowing the trick does not turn the trick off. It puts a handle on it.

Down the stair, the basement door is a dark mouth. The tide-clock is down there, skipping, Tess said, like a heart that cannot count. Up here, the gallery door opens to a wet rail and a better chart.