When Dani Nowak spots what looks like a World War II era German U-boat, presumed lost at sea for more than eighty years, cutting through the twilight waters off the Gulf Coast of Florida, she is tossed between the whispering ghosts of her family's tragic history in occupied Poland and the increasingly grim realities that confront her and her colleagues as they search across time and thousands of miles for the "ghost ship" U-925 and the terrifying secrets that it might still hold.