Four years after the events of The Final Reckoning, midshipmouse Thomas Triton is troubled by memories of a traumatic incident in his youth that resulted in the death of his best friend, Woodget Pipple.

Thomas vows to find Woodget, and catches up with him at a dock as a ship called the Calliope is getting ready to set sail.

Dimlon drops his facade of innocence and reveals himself to Mulligan as Dahrem Ruhar, an adept of the Scale, an evil cult that worships a banished reptile god called Suruth Scarophion.

After they explain the situation, the mongooses offer to take the two mice to Hara, their home city in India so they can speak to the sadhu and ask his advice.

Upon their arrival in Hara, Thomas, Woodget and mongoose Captain Chattan go to see the sadhu, who also possesses a piece of the jade egg of Scarophion.

Chattan engages in battle with Dahrem, who demonstrates his ability as an adept to tear his mammalian flesh off and assume the form of a lizard.

The bar is full of members of the cult (including Ma Skillet, the high priestess) who capture Thomas, Woodget, and Simoon and take them to their temple.

Simoon reveals that it was the plan all along to let the Scale obtain every piece of the egg, as he and other members of the Green Council like the sadhu knew it would ultimately be useless.

The fragment held by Mulligan was periodically moved to different shrines to the benevolent Green Mouse deity, and thus gradually became a holy object.

"[2] Zenna, the siren who becomes infatuated with Woodget after he defends her from her mocking sisters, was named after the daughter of a librarian Jarvis met when he visited her school in Shropshire.

[3] Regarding Thomas, Ilene Cooper of Booklist said "its archaic sentence structures and florid word choices are problematic, but series fans probably won't mind.