Kakababu, whose heart quickened at clues, read. The notebook belonged to Samar Prakash—S.P.—a surveyor who had worked mapping the Sundarbans in 1939. The entries spoke of tidal calculations and mangrove markers, but tucked among charts were odd notes: a promised meeting with a man called “Ravi,” a reference to a “portable” that would keep something safe, and, toward the back, a map with an X beneath the inked words: Old Pagla Island.