At first, the tapping seemed to follow Isla wherever she went. In the kitchen it was a faint tick; in the hallway it became a sharper knock. Upstairs, beside the unused bedroom, she could hardly hear it at all.
Her brother suggested a loose shutter. Isla went outside and looked up. Every shutter was still. The tapping continued even when the wind dropped, so she crossed that idea off the list she had started in her notebook.
They walked through the house again. This time, Isla marked the places where the sound was loudest. All three were close to the pipe that ran behind the hallway wall. Her brother listened while she turned off the kitchen tap. For a moment, the sound stopped. Then it returned when the tap was opened.
Their father listened to the recording they had made and said he would arrange for someone to check the pipe. Isla was disappointed. She had hoped to discover a hidden room or an animal nesting somewhere unusual.
That evening, her brother pointed to the notebook. “You still found out something,” he said. “You didn’t start with the pipe.”
Isla added one final line: Sound changes when the tap changes. She left the word “cause” out of it. They had found a useful connection, but a person who knew about pipes would need to decide what was actually happening. Closing the notebook felt less dramatic than opening a secret door, yet it felt more satisfying than she had expected.