|“||Then let's chop them around a bit, slit their throats, then go back to Torca Marda to claim our reward||„|
|“||I thought you two were dead||„|
|~ The reaction to everyone who sees the two ferrets|
They reappear in the final book Windjammer Run as the tertiary antagonists.
The two evil ferrets are encountered first at the titular Castle Storm, where they appear to have done well out of the stoat rule. All other creatures are enslaved by the cruel stoats, but only spies, lords, and traitors do well out of the recession and the slavery. The ferrets are somewhat affable towards Sylver and his weasels, and they suggest many ways of assassination. Bryony, one weasel, jokes that they were discussing the ways of killing a spy ferret that fell into their clutches which disgusts Guildenswine.
Rosencrass & Guildenswine, bold as they are, are terrified of Torca Marda - at least Rosencrass is, he gulps when he sees the priest. The two evil ferrets are witnessed in the dark tunnels beneath the castle, helping Torca Marda do dark magic to resurrect a deceased, deformed badger. The ferrets demand payment for a dirty job.
Afterwards, when Torca Marda gets wind of the weasels' quest for the herb to stop the carnivorous dragonfly from eating the squirrels, Torca Marda sends Rosencrass & Guildenswine to kill Sylver and his friends. Rosencrass & Guildenswine take the same route Sylver took. They run into a band of ptarmigan birds who are obsessed with braeburn apples, and whereas the outlaw weasels supported their claims promising to come back with apples, the treacherous ferrets got annoyed with Robbie, one bird, pestering them about apples, they strangled him to death, and Rosencrass hissed "What about them apples?" when he watched Robbie die.
This proves their downfall - when the two ferrets capture Sylver and his friends in the Forest of Lost Birds, the ferrets do not know that the Forest is omniscient and sentient, and punishes anyone who damages nature. So, when Rosencrass confesses that he and Guildenswine killed a bird, the Forest entombs the two ferrets in a tree in a dramatic fashion by having the tree branches come to life and drag them away.
Now stuck as part of a tree, the terrified ferrets have no hope of rescue. However, they are still alive. Sylver thinks a human may chop down the tree and put the ferrets on his mantelpiece. However, Torca Marda believes the weasels ambushed the ferrets and brutally murdered them, but this is a lie. Torca Marda threatens to kill or imprison the weasels, but is desisted once he is proven to be a liar. Sheriff Falshed is sent to find evidence, he does find the entombed ferrets, and on his return is conceiving a lie to doom the weasels but he actually realizes Torca Marda would never reward him and he tells the truth, that the weasels were right. Torca Marda throws Falshed in jail but he joins the weasels and escapes.
However, sometime in the events between the two books, Castle Storm and Windjammer Run, the tree that entombed Rosencrass & Guildenswine was somehow chopped down and turned into a windjammer ship to chase Sylver and became Sheriff Falshed's ship. Rosencrass & Guildenswine were made into a figurehead, albeit a living, talking figurehead. Their "freedom" from the tree made them regain their ability of speech.
Their progress to stop Sylver was not pleasant. They were actually reunited with the ptarmigan birds, the same ones that they had killed their cousin Robbie, and the ptarmigan threatened to mutilate the ferrets if they mocked him. The two ferrets were very annoying during the quest to find Sylver, making up lies about sea monsters and the like. They got threatened with death several times, Falshed said he'd send them to "Duffy Jonah's Locker."
Rosencrass & Guildenswine presumably lured Falshed to wreck Sylver's ship and forced him to build a new one.
In return, Falshed abandoned the two sly ferrets on a colony of mongeese as Falshed had gone about conquering and making deals with the inhabitants to abide by Prince Poynt's laws. The shocked ferrets were left entombed in their bark, prompted to tell the upcoming weather to the superstitious mongeese.