Some theories put forward over the years concerning the Mary Celeste have included:
The entire crew may have been swept overboard (assuming that one of them must have been carrying the chronometer and ship's papers at the time) by a large wave while watching their delirious (or drunken), fully-dressed, captain swimming around the vessel in mid-ocean with his daughter on his back (You can be sure that Mrs. Captain had something to say about that!).
The Mary Celeste came to the aid of a burning cargo ship filled with coal and explosives. The Mary Celeste got a little too close to the burning ship and the crew abandoned ship into a small lifeboat which also picked up the crew of the cargo ship. The lifeboat then capsized and all hands were lost. Unfortunately there isn't any record of a cargo ship being lost during that period and some have reported that the single lifeboat was still onboard the Mary Celeste.
The captain of the Dei Gratia, the ship which found and applied for salvage rights to the Mary Celeste, hatched a plot to takeover the ship by placing three of his cut throats on the Mary Celeste as crewmen. Once at sea, the crewmen overtook the vessel and killed the captain and crew. The Dei Gratia then "discovered" the "abandoned" vessel and claimed salvage rights to the ship and the cargo.
What is the real story of the Mary Celeste? What was the fate of Captain Briggs and his family, and the crew of the Mary Celeste... nobody knows?