Blood Vessel - S1-E2
Trivia: The secretive room on the ship with a dark secret is cabin no. 9. Mark Gatiss, co-writer of this series, also co-wrote another creepy BBC series called "Inside No. 9"
Trivia: The character of Dani Clayton is named after Jack Clayton, who directed "The Innocents." "The Innocents" is the film adaptation of the stage version of Henry James' "The Turn of the Screw." (Source: ScreenRant).