Seasparrow. Graceling Realm #5

Seasparrow is the 5th book in the Graceling Realm Series.

The fifth novel in the bestselling Graceling Realm series is told from the point of view of Hava, Queen Bitterblue's sister and spy, and chronicles the harrowing journey back to Monsea.

Hava sails across the sea toward Monsea with her sister, the royal entourage, and the world's only copies of the formulas for the zilfium weapon she saved at the end of Winterkeep. During the crossing, Hava makes an unexpected discovery about one of the ship's crew, but before she can unravel the mystery, storms drive their ship off course, wrecking them in the ice far north of the Royal Continent. The survivors must endure a harrowing trek across the ice to make it back to Monsea. And while Queen Bitterblue grapples with how to carry the responsibility of a weapon that will change the world, Hava has a few more mysteries to solve and a decision to make about who she wants to be in the new world Bitterblue will build.