What really happened on board of the Titanic?

Someone, or something, is haunting the ship. Between unexplained disappearances and eerie deaths, the guests of the Titanic-particularly maid Annie Hebley and guest Mark Fletcher-are convinced there's something sinister afoot. But before they can unveil the danger that beckons them, disaster strikes.

Years later, Annie is working as a nurse on the sixth voyage of the Titanic's sister ship, the Britannic, newly refitted as a hospital ship. When she happens across an unconscious Mark, now a soldier fighting in World War I, Annie is relieved to see he survived the sinking. But soon Mark's presence awakens deep-buried secrets, a creeping darkness forcing Annie to reckon with the demons of her past-as they both discover the terror may not yet be over.