Hope is an anchor, and Natalie Morrigan is drowning. Haunted by a power she can't control, Natalie and her friends are determined to reunite their families and uncover the truth of their past. But with Leo missing in action and Uncle Chris out of the picture, Natalie is left harboring a mysterious key and a secret that isn't hers to tell. Invited to masquerade as a Nautilus recruit, Natalie finds herself in the Helix: Nautilus's center...