Spoiler alert! The following post contains important details about the end of “The Last Voyage of the Demeter” (now in theaters).

All aboard the Dracula boat.

“The Last Voyage of the Demeter” has set sail in theaters, earning frightful reviews while sparking some amusing memes for its dopey premise. An “Alien” riff on the high seas, the movie is set on a London-bound cargo ship in 1893 where Dracula is stowed away. One by one, the fearsome vampire starts picking off members of the crew, sending a pragmatic doctor named Clemens (Corey Hawkins) on a desperate hunt for answers.

Here’s how the film differs from its classic source material:

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What is 'The Last Voyage of the Demeter' movie based on?

The film is loosely adapted from Bram Stoker’s 1897 novel “Dracula,” specifically the seventh chapter. In the book, the Demeter ship runs aground on the beach of an English coastal town after a terrible storm. Local police and coast guard climb aboard to discover that the entire crew is missing save for the dead captain, who is tied to the ship's wheel.

They manage to find the captain’s logbook, which briefly recounts the mysterious events from his perspective. According to the captain’s account, a crewmate reported seeing “a tall, thin man” on the ship, although no one was able to find him. Every few days, a member of the crew would disappear, until one foggy night when only the captain and one other sailor remained.

After witnessing something horrifying below deck, the sailor threw himself into the ocean, screaming, “The sea will save me from Him, and it is all that is left!” Resigned to his fate, the caption fastened himself to the wheel of the Demeter: choosing to go down with honor and face whatever monster has claimed his men.

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What's different in the new Dracula movie?

Because the film is based on just a handful of pages from the book, most of “The Last Voyage of the Demeter” is new. Clemens is not featured in the novel, nor are the movie’s other protagonists: Anna (Aisling Franciosi), a stowaway from Transylvania who helps Clemens fight Dracula; and Toby (Woody Norman), the affable young grandson of Captain Elliot (Liam Cunningham) who is killed by the vampire.

In the book, the ship's crew vanish without a trace. But here, each person's killing is shown in grisly detail, and Clemens finds the bloody evidence of their murders. The movie features extended storylines about Dracula ravaging the boat’s livestock, and Clemens attempting blood transfusions to save his injured shipmates. Clemens and Anna also do battle with Dracula in the film's effects-heavy climax, as they try unsuccessfully to trap him on the ship.

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What's the ending of 'The Last Voyage of the Demeter?'

In the novel, Dracula transforms into a giant dog and runs off the Demeter when it crashes ashore. That part is omitted from the movie, although we do see a cloaked Dracula again in the final scene.

Although there are no survivors from the Demeter in the book, the movie makes one major change by letting Clemens live. After the captain’s death, he jumps ship and floats back to the mainland on a piece of debris. Sitting in a tavern at the end of the film, he spots Dracula in a corner of the bar and chases after him, vowing to kill the monster in an apparent bid for a second movie. But the thriller’s dire box-office receipts will likely drive a stake in any sequel hopes. Sucks to be Dracula, right?