The Caldera

The crown prince of Byzantos has been kidnapped by a pirate fleet based in the caldera of a dead volcano — a ring of high cliffs around a sheltered bay, with one narrow entrance and a chain across it. The Herons are hired to find him and get him out. The chain is the easy problem.

The Caldera is a compact rescue-thriller with the kind of ship-design-versus-fortification problem the series has always been good at. The Heron’s small size turns from disadvantage to the only thing that lets the plan work.