Suspicion, hidden loyalties, and devious strategy rule the day! Unfathomable puts the players in command of a steamship, but not every player can be trusted. While monstrous Deep Ones stream forth from the crushing ocean depths, any player could secretly be a nefarious cultist or a horrifying hybrid Deep One. The investigators must take care not to turn their backs on anyoneit will take all their cunning to save their ship from a watery grave. Battle swarming Deep Ones, uncover the traitors, and steer the Atlantica safely home in Unfathomable!