Sasha is sent back on the hired boat with the loot gathered thus far: some notes and the golden sphere. Everyone else regroups to figure out what to do, and eventually decide to go see John Courage and propose working together to rescue Ivar and recover any other notes that need recovering.
John is staying in an expensive inn, and has wine sent up when they arrive. He agrees to help, and tries to arrange for an entire copy of the recovered notes. Team Unicorn points out that they could have left him in the treasury to be captured, but hauled him out, and he gives in and agrees to help for a copy of one page, randomly selected, from the notes, and the return of his codebook. He then provides the plan, which is generally agreed to, and spends the next day in meditation to get enough magical power to implement it. The team is left to arrange the other pieces of the plan.
The next night they put the plan into action. John goes into a divinatory trance (blindfolded), and guides them into the castle. They walk past the gate guards just as they are all distracted by a delivery. They pause just before patrols arrive, and coast behind turned backs. It's impressive magic, though not magic John could have done by himself - Lucia has to take his arm and guide him past the merely physical obstacles.
They come to the first important point, and encounter Mirella Estrella returning to her guest room from the bath. They're pretending to be tailors, and while John "the blind tailor" takes her measurements behind a screen for the new gown that the Duke is getting her, the others rifle her possessions, locating the extra notes. Lucia leaves behind some blank paper in their hiding place. Then they have to make John stop measuring and get back to guiding them.
Which brings them to Ivar... Ivar has spent the past day being tortured by the Duke, who is unconvinced that he is innocent. It appears that Jeppo broke pretty much instantly after being brought in and fingered the team as Daran spies. Ivar keeps playing dumb, but is having trouble... they have placed him in an iron cage which is periodically lowered into the water, where Ivar struggles not to drown and is attacked by bitey fish. When the rest of the team arrives, he has been left under guard to consider perhaps being more cooperative.
Baba and Gaius are able to fight the guards back towards Ivar's cage, and the barbarian seizes one in his strong arms and throws him off the ledge and into the waters below. At this, the other surrenders. Ivar then batters his way out of the cage, and they put the final part of the plan in action. First, John gets a copy of one of the pages. Then they strap themselves to dandelion seeds (magical flying machines) and leap out of the castle. The prevailing winds take them a mile or so out to sea, where a ship is waiting. Baba and Lucia land in the water, but are recovered. John is blown away by an errant breeze who knows where.
After that it's pretty much all cleanup. They return to HQ. The sphere and notes are given back to the Golden Lion guild, and copies are also quietly disseminated to their chief rivals in order to further arcanology as fast as possible. The general thrust of the notes is to detail techniques to use spells on spells, allowing for spells which increase the effect, duration, and range of other spells. The sphere is a general amplifier for force spells, as a demonstration.
The page that John ended up with was a very important page, so it is expected that the Miskans will be able to duplicate this research with time, but for now the Empire has a good head start. John's codebook is returned to the Miskans much later, by post, with Group 23 having made a copy of the whole thing.