A Storm in Every Heart by Kate King

Here is a summary with spoilers for A Storm in Every Heart by Kate King

As a child, Odessa lived on the sea with her parents. As a part-siren, the ocean called to her, but she was taken away when her parents died and sent to live with her closest family members. This left her with her cousin Daemon, a bastard son of the royal king. The two basically became siblings, and together, one of their first interactions is with a young boy who bets them both on a fight and ends up winning. Odessa is drawn to the boy, and before he leaves, she gives him her key necklace. She has a suspicion that the boy was royalty.

Back in the present, Odessa has found her place. She loves living in the castle, even if her brother and now-former prince Kastian live there as well. But her life changes when King Magnus from the neighboring land comes to make a bargain with them. His price for safety is having Odessa as his betrothed. While they all assure her she has a choice, Odessa agrees, feeling like her life needs something. And while she is going under the terms of a betrothal, she really wants to know what this king has to offer her people. Kastian, though, doesn’t like this at all, because while he likes to pretend otherwise, he is truly obsessed with Odessa.

In the past, the kingdom holds a set of festivities while the royals are searching for a wedding match. This leads Daemon and Odessa to travel to another kingdom, where Odessa finds the boy from her childhood. He is indeed Prince Kastian Stormbreaker. The two bump into each other, and she is very rude to Kastian, but he doesn’t recognize her. Because she is playing hard to get, he becomes even more entranced and keeps trying to get closer to her. Eventually, the two end up betting again, and this time Odessa wins. She wants him to take her to the docks so she can see the ships. While there, she drops some hints, and Kastian finally realizes who Odessa is and even tells her he kept the key.

In the present, the night before Odessa leaves, Kastian comes to her and lays himself bare. The two end up sleeping together, but Odessa insists it is a one-time thing. She sneaks out in the morning and, without saying goodbye to anyone, leaves for her journey. While on the train, they are attacked and taken by an immortal pirate, Captain Connell. When Kastian learns that Odessa left in the morning, he goes after her, finds the wrecked train, and ends up discovering her on the pirate’s ship. During the fight to save her, a sea monster attacks, forcing Kastian and Odessa to abandon ship. They take Captain Connell with them to later interrogate him. The group wanders through the forest, chased by guards, all while trying to find safety.

In the past, Odessa is scared of the pull she feels toward Kastian and ends up using her siren song on him, telling him to never look for her and to go away. However, that night, Odessa overhears King Magnus talking about a coup and how they plan to kill Kastian and his family. When Odessa goes to look for Kastian, she doesn’t find him until it’s too late. His betrothed, Lyra, has already drugged him and pushed him overboard. Odessa jumps in after him and turns into a siren. The sirens, including the Siren Queen, come for her and make a deal to save Kastian. He will lose all his memories of her, she is not allowed to speak of their past, and she must return to the sea at some point in her life.

As the group continues searching for safety, Odessa and Kastian are left alone for a while, and after an intimate moment, they realize they are mates. They don’t get to celebrate for long, as soldiers capture them and take them straight to King Magnus. Odessa meets him, and he tells her they are to be married. Meanwhile, Kastian is thrown into prison and tortured to death, which Odessa hears about and is devastated. While Kastian does die, he is brought back by his friend Jett and Captain Connell. In desperation, Captain Connell offers a deal: Kastian can become the new captain of his ship. By doing so, he will be immortal but must spend six months of each year on the ship. Kastian agrees, is restored, and goes straight for Odessa.

Odessa is about to give herself to the sea to complete her bargain when Kastian finds her and watches as she is pulled underwater. Kastian dives after her, and together they fight the Siren Queen, ultimately banishing her. It becomes clear that Odessa could become the new Queen of the Sirens, but she doesn’t want that. Lyra, who helped both Odessa and Kastian escape King Magnus, becomes a new leader instead, while King Magnus himself is now being tortured.

Kastian and Odessa get to live their happily ever after, spending half the year on the ship and half the year on land. The two love every second of it, even though it means time away from friends and family.