The secrets of the heart lie in uncharted waters.

Captain Nisha "Nemo" Majhi is on a mission. If her submarine, the Narwhal, can complete a week-long test run—without surfacing—she'll earn the sponsorship she needs to explore the Great Lakes and beyond. She'll let nothing thwart her dream of scientific advancement. Not even an intriguing and handsome accidental passenger.

All Aleksy Szekalski meant to do was rescue an animal in need. He never intended to stumble onto a departing ship. And he certainly doesn't want to spend a week underwater with a strange woman. Even if she is clever and pretty and—worst of all—as excited by scientific discoveries as he is.

In the close confines of the submarine, Nemo and Aleksy grow from strangers to friends to lovers. But above the surface, a ruthless adversary hunts the Narwhal. With enemies on their tail, Nemo and Aleksy race through the lakes, encountering pirates, mechanical monsters, and secrets deep below the waves. To survive the treacherous waters, they'll need sharp wits, expert skills, and above all, an unsinkable partnership.