The story of 'The Last Voyage of the Demeter' being based on a true story has its roots in the Dracula lore. In Bram Stoker's original work, the Demeter is the ship that brings Dracula to England. The movie or other adaptations that focus on this last voyage take that nugget of truth from the classic novel and expand on it. They show the horrors that the crew of the Demeter must have faced during that journey, with Dracula preying on them as they cross the sea. It's a really interesting exploration of that small part of the larger Dracula story.
It's about the ill - fated voyage of the Demeter. The Demeter was a ship that carried Dracula in the story. The crew faced many terrors during the journey, with strange disappearances and a sense of doom. Dracula was on board, preying on the crew one by one.
The central character is Dracula, who is on board the Demeter. He is the one causing all the mayhem. The crew of the Demeter are also main characters in a way. They experience the horror first - hand. They start as normal sailors but are gradually terrorized by Dracula. For example, the captain who has to deal with the strange happenings on the ship and the sailors who try to figure out what's going on and ultimately fall victim to Dracula's thirst for blood.
The Demeter was a ship in Bram Stoker's 'Dracula'. In the story, it carried Dracula from Transylvania to England. The crew mysteriously started to disappear one by one during the voyage. Eventually, the ship crashed ashore with no living crew left, save for the captain, who was found tied to the wheel, dead. It was a very spooky and mysterious part of the Dracula narrative.
I'm not sure specifically as I haven't read it in detail. But generally, it might be about a ship's final journey where there are some spooky or mysterious elements associated with it, like strange sightings on board or some unexplained events that led to it being considered a 'ghost ship' during this last voyage.
As I said before, without knowing which 'the Demeter true story' it is, it's hard to say. But if it's about the Demeter in Greek mythology, key elements would be her role as the goddess of the harvest, her relationship with her daughter Persephone, and how the abduction of Persephone affected the world in terms of seasons.