Hearts of Pandora. Book 11

Hiding from the chase at the Lyutvidzh academy, Oz and his company tell Leim about the betrayal of Duke Balma.
However, it soon becomes clear that things are not so simple, as it was Balma who sent his subordinate to... help Oz. What goal does the capricious duke pursue? Why did he put the key in Leim's pocket? Oz Bezal is sure that there should be a door for every key. The only question left is which one — for the academy is full of corridors and secret passages.
And time is running out: if the friends do not figure out what Balma aims for, the Baskervilles will execute Blake and the grandmother and granddaughter Rainsworth, who are stripped of the power of their Chains…
The book includes volumes 21 and 22 (chapters 83–92 + bonus).