The merchant ship Demeter, under the command of its captain, sets sail from the Mediterranean for England. On board are the doctor Clemens, Wojchek (the first mate), Toby (the captain's grandson), and a small crew of sailors. They are carrying numerous barrels of strange sand. While the captain initially reports calm seas in his logbook, strange occurrences soon begin to multiply. Not only does the crew discover a stowaway named Anna on board, but after a few days, one sailor after another disappears.