Eryx, a deckhand aboard the Iron Heart, has long accepted the harsh life at sea under the fearsome Captain Blackhart. Keeping to himself, Eryx knows his place-until the crew captures a mermaid. Stolen from the waves, the mermaid becomes a prisoner, unable to return to the ocean. Her presence is said to protect against sea monsters and sirens, but Blackhart sees only the wealth she could bring as a prize for the King of Kaldur.
In exchange for her freedom, the mermaid strikes a deal with Blackhart: she will lead him to the long-lost wreck of the Fidelis, a ship fabled to carry unimaginable riches. The crew is eager for the promised treasure, but Eryx, the only one who notices the mermaid's quiet suffering, finds himself drawn to her. As he secretly tends to her wounds, a bond forms between them, forcing Eryx to question his role on the ship and his loyalty to a captain consumed by greed.
As the Iron Heart sails ever closer to the treasure, the journey becomes perilous. The sea grows restless, its winds carrying whispers of curses and ancient powers. Eryx senses a danger far greater than the treasure they seek-a force stirring beneath the waves, tied to the mermaid and the Fidelis. Torn between his duty to the crew and his desire to help the mermaid escape, Eryx faces a choice that could doom them all.
With the Iron Heart on the brink of finding the fabled wreck, Eryx must decide where his allegiance truly lies-whether some treasures are worth the cost of freedom. But the sea never forgets what it's lost, and it always demands a price.