A ghost ship named Mary Celeste was abandoned in the coasts of Portugal in 1872. It was known to have been travelling from Newyork to Genoa, Italy. Several theories have been proposed as to what caused the abandon. The passage explains two of the possibilities, "A Mutiny" and "A Piracy".
The passage says that the Captain of Mary Celeste, Benjamin Briggs was overly strict which made his crew members to kill the captain and his family and throw them into the sea. But the lecture contrasts this by saying that the Captain was an experienced and a respected person who was in charge of his crew and had freindly relationships with them.
The passage suggests another possibility could be that the ship which found the Mary Celeste killed the crew and the passengers for greed of valuables and threw them overboard to erase any evidence and later took the ship to Gibralter to claim a prize for finding the abandoned ship. This theory too, is countered by the lecture. It says that niether did the passengers carry any valuables which led to piracy, nor did the court find any evidence against Dae E Gracias who found the ship. Also the captains of both the ships were found to be in good terms.
The lecture gives one plausible expalnation , since both the passage and the lecture agree with the fact that out of 1701 barrels of alcohol that were carried, 9 were found empty. The barrels of alcohol would have been emptied due to leakage which led to fumes. Captain Briggs feared an explosion from these fumes, He feared a fire most as never before had they exported alcohol. This also explains the opened hatches and portholes. Hence they fled on a life boat and got lost in the sea either due to starvation or falling prey to the storm.