The year is 1908. 17-year-old Rosalind's father has booked Rosalind on the maiden voyage of his Transatlantic Express, the world's first railroad to travel under the sea, without asking. Rosalind is furious. Cecily and her brother Charles volunteer to accompany her home from England. Then, deep under the Atlantic, Cecily and her housemaid, Doris, are found stabbed to death in their state room. Rosalind is now trapped on the train - where nothing is as it seems - in a deadly fight to clear herself of her friend's murder and to thwart a sinister enemy whose ambitions she can only imagine.