There was something aboard

"On 16 July mate reported in the morning that one of the crew, Petrofsky, was missing. Could not account for it. Took larboard watch eight bells last night, was relieved by Amramoff, but did not go to bunk. Men more downcast than ever. All said they expected something of the kind, but would not say more than there was SOMETHING aboard."
-- Dracula, Bram Stoker (1897)
Dracula, Bram Stoker (1897) The Demeter is the Russian ship that brings Dracula to England. During the voyage the vampire sustains himself on the crew, picking them off one by one until only the captain remains.

Star Trek, 'Where No Man Has Gone Before' (1969) Samuel A. Peeples, Gene Roddenberry. Two crew members become invested with terrifying mental powers. As their abilities grow they lose all human empathy and threaten the crew.

Alien (1979). Dan O'Bannon, Ronald Shusett. An alien infects a crewmember, hatches on board the vessel and infests it, feeding off her crew.

Firefly, 'Our Mrs Reynolds' Joss Whedon: (2002) A stowaway con artist overcomes the captain and crew, betraying the vessel to her cohorts.

The Star Trek and Firefly episodes are two of the most satisfying of their respective series. In each, the antagonist's actions force the protagonists to reveal their character through action. By the end the audience requires no further introduction to the characters: the exposition is an integral part of the drama, and the story is complete.