The fourth book, "Secrets of the Fire Sea", is a murder mystery set on the island of Jago (in the Fire Sea of the title), and features the consulting detective Jethro Daunt and his steamman assistant Boxiron attempting to uncover the murderer of the island's arch-bishop. Commodore Black ferries the investigators from the kingdom to Jago, and acts as a reluctant foil for the pair's sleuthing. The novel was published in the UK as a hardback in 2010 and as a paperback in 2011.