The Earth-Fae treaty is almost complete when rogue highborns halt negotiations.
In an effort to discover why cooperation failed, the ambassadors agree to spy. Before they can uncover the lords' plot, the ambassadors are imprisoned or disappear.

Determined to save the treaty, the prince finally comes out of hiding.
But his enemies already tried to assassinate him and will surely try again. Even if his allies can protect him, they first must rescue the ambassadors to prevent them from becoming hostages when he claims his throne.

But the lords declare him an imposter and command the fae to conquer Earth.
Contemporary YA fantasy with a dash of sci fi & mythology, from the author of Unexpected Heroes.