What destroys the Mortzestus? A mass of spectral sailors boards the vessel as a huge ghost ship converges with it. The exact physical mechanism is unclear, but the Mortzestus sinks or vanishes during the encounter.
How does Jessop survive? He gets clear of the ship during the final assault and remains afloat until the Sangier finds him. Its captain and officers add a formal statement confirming the rescue and the Mortzestus's loss.
What are the ghost pirates? The novel never defines them. They appear to be the crews of vessels existing beyond a weakened barrier between material and immaterial worlds, able to become increasingly physical around the Mortzestus.
Was Jessop's theory correct? It is the closest the book comes to an explanation: the haunted ship has somehow become accessible from another plane. The final events support the theory without proving its mechanics.
What does the official record say? It rationalises everything away: the Mortzestus is entered in the books as simply unseaworthy and foundered. The one corroboration Jessop has is that the Sangier's crew, close by and unseen the whole time, heard the screams of the dying men.
Themes and What the Ending Means
The failure of ordinary explanations Each rational excuse works briefly—stowaway, prank, bad seamanship, panic—but repeated evidence makes denial more dangerous than belief.
Work invaded by the supernatural The haunting manipulates sails, ropes, watches, and steering. Horror enters through routine labor rather than interrupting it from outside.
Visibility and isolation Different men can stand together and perceive different lights or ships. The inability to share sight fractures the crew before the attackers physically separate them.
Authority under pressure Officers must decide when testimony deserves action. Skepticism protects discipline at first but later delays collective recognition of danger.
The sea as boundary The ocean is not merely a setting but a surface between worlds, allowing figures and vessels to rise from an unseen realm.