The ferry ran the Pell Island crossing twice a day for sixty years without losing a soul. The discrepancy on the last evening run of the season — forty-one tickets sold, forty passengers ashore — was logged as a counting error and forgotten for three decades.
It was not a counting error. The answer was sitting in the harbourmaster's own records the entire time, in a detail everyone had read and no one had questioned.
This case is closed. The full account of how it was solved goes here, with the documents that broke it open.