A few moments later, the sea changed quickly.

The once smooth surface rippled with unrest, shadows weaving beneath the foam as the sky began to darken—not with clouds, but with a strange heaviness that seemed to press down on the world. The wind kicked up without warning, shrieking against the boat's metal frame like a warning howl from the deep.

Callista felt it before she saw it. A lurch beneath her feet, a sudden roll of the deck that made her stomach flip. Her fingers dug tighter into the ...