Dr. Stanley Colton seeks sleep at a remote seaside point but is drawn into strange nocturnal phenomena after meeting the fastidious Professor Ravenden. What begins as curious observations and searches for unusual natural specimens escalates into disturbing discoveries — a sea‑waif, a body associated with a buoy, urgent cries after dusk — and a piecing together of contradictory clues. The narrative tracks their methodical inquiry, moments of terror and misdirection, and gradual readjustments of evidence and theory, leading to a final confrontation that reveals hidden connections and a lone survivor’s fate.