On August 6, 1897, the merchant ship Demeter washes ashore in England. Among the wreckage found by the police is the log kept by her captain, Eliot.One month earlier, the Demeter makes port in Varna, Bulgaria, to pick up cargo for transportation to London. The shipment, consisting of multiple large wooden crates, is transported by locals from Romania. However, the locals refuse to load the cargo onto the ship, insisting that they must leave the area before sundown. One of them hands the quartermaster, Wojchek, and another crewman, Olgaren, a large sum of money and wishes the Demeter a safe voyage before departing with the others.Clemens, a doctor educated at the University of Cambridge, overhears that the ship is looking for crewmen. He attempts to convince the crew that his medical skills and knowledge of astronomy would make him a valuable asset to them. Wojchek rejects him and hires an older man instead, but while helping to load one of the crates, the new hire - frightened upon recognizing the dragon emblem on its shorter side - accidentally releases the tackle rope, causing the crate to fall. Clemens witnesses the accident and saves Eliot's grandson, Toby, from being crushed by the loose crate. The new hire declares the dragon emblem a bad omen and leaves; out of gratitude for Clemens' intervention, Eliot hires him as a replacement.One of the crates falls and breaks open in the cargo hold. Clemens investigates and finds a woman buried in dirt inside. She is barely alive, and he performs blood transfusions on her to treat what he believes to be an infection. Later in the Aegean Sea, Clemens and Olgaren see a mysterious figure in the fog on deck.The next night, all the animals aboard the ship are killed, including the ship's dog, Huckleberry. The crew, fearing a rabies outbreak, throws them all overboard. Anna, the secret stowaway, wakes up and warns them about a monster from Transylvania, a creature that feeds on the blood of humans. In her town they called it Dracula, to whom she was given as a slave of blood so that the monster would leave them alone. She claims that Dracula is already aboard the ship and looking to feed, revealing several bites on her body.Dracula hunts the crew during the night, biting Olgaren and turning him into a vampiric thrall. Olgaren is temporarily restrained, tied to a table; he breaks free, and, seeing Toby in the hold, begins hunting the boy and traps him in the captain's quarters, along with Dracula. As the crew attempts to save him, Toby is bitten by Dracula. The next morning, the vampiric Olgaren, who had been tied to the mast by the crew, bursts into flames as the sun rises. Despite blood transfusions from his grandfather, Toby dies, and is wrapped in parts of the sailcloth for his sea-burial. During the funeral, the captain believes he sees Toby moving; he unwraps him, only for Toby to suddenly attack. The vampiric Toby catches fire in the sunlight (also severely burning his grandfather) before Clemens is able to throw him into the ocean.The remaining crew want to destroy the ship and drown Dracula to prevent him from causing chaos once they reach London. Captain Eliot, Abrams, and Wojchek are killed by Dracula, and Anna is bitten during an attempt to save Clemens. Clemens rescues Anna by hitting Dracula with an axe, and Anna manages to crush Dracula with a part of the mast. Anna and Clemens jump ship, thinking the vampire is dead; before sinking, the ship ends up running aground on the British coast, enabling Dracula to push the mast off of his body, roaring in victory.Anna and Clemens float away on debris, and she reveals to Clemens that she is becoming a vampire after Dracula's bite; Clemens' blood transfusions only delay the change. As the day dawns, and not wanting to become a monster, Anna willingly immolates herself in the sunrise as Clemens drifts ashore.Arriving in London, Clemens goes to a local tavern where he draws Anna's portrait in his notebook. He hears the knocking signal from the Demeter's crew of "all clear", and then sees Dracula, dressed as an aristocrat, laughing at him; the vampire disappears. Leaving the pub, Clemens sees Dracula's shadow and follows him; he vows, for the memory and honour of his dead companions, that he will kill Dracula and send him back to Hell.