Royal Twins Shalin & Esme Book 5 Greek Fire

A royal summons from her father, King Blackwell, has medical student Princess Esme traveling from Helsop back to her home in Henge. Cousin Electra decides to go with her to travel on past Henge to Fernland to visit her mother, Queen Delphinia. But why does Headman Dagon of Helsop suggest his two sons, Gregor and Soren go along with them?
Esme knows the answer to this since she can read minds.

Secrets abound in this small corner of the world. Serafina hopes to reinvent the fearsome weapon, Greek fire and decides the Imperial Library in Constantinople is the best place to do her research. Usually her husband King Blackwell would forbid such a long journey but this time he is in favor of it. He wants his lineage to carry royal blood on both sides. The royal twins, Shalin and Electra, have other ideas.