Between mysterious disappearances and sudden deaths, the guests of the Titanic have found  themselves suspended in an eerie, unsettling twilight zone. Several of them, including maid Annie Hebley, guest Mark Fletcher, and millionaires Madeleine Astor and Benjamin Guggenheim, are convinced there's something sinister --- almost otherwordly --- afoot. But before they can locate the source of the danger, disaster strikes. Years later, Annie, having survived that fateful night, goes to work as a nurse on the sixth sailing of the Britannic, newly refitted as a hospital ship. When she happens across an unconscious Mark, now a soldier fighting in World War I, she is forced to reckon with the demons of her past --- as they both discover that the terror may not yet be over.