On the first morning of summer, Pip ran down to the beach and almost tripped over her dog Biscuit. He had a green bottle in his jaws, washed up between two rocks. Pip pried it open. Inside was a paper torn down the middle: half a coastline in faded blue ink, and one word left at the rip. It said HARBOR.

Pip studied the faded ink instead of rushing off. The half-coastline matched the bay in front of her, but it showed a small cove that wasn't on any modern map. She decided to follow the inked shoreline on foot, hugging the rocks, to find the cove the mapmaker drew.