Old Chen goes to the abandoned lighthouse every evening. The administrator says it's haunted, but he always arranges three pebbles in the wooden box on the top floor. Until the demolition team dug out a rusted iron box, the yellowed letter paper revealed faded writing: "On the night of the typhoon in 1943, hide away the three baby teeth of my daughter." Old Chen suddenly coughed violently, and in his palm lay a blood-stained molar—he had guarded the lighthouse for sixty years, which was originally the coordinate to guide his lost daughter home.