Castle Storm is the second novel in the Welkin Weasels series by Garry Kilworth. Picking up shortly after the end of Thunder Oak, the novel centres on the anthropomorphised weasels searching for the humans that mysteriously vanished from their homeland many years before. Following a clue found in the first book, the weasels, led by the outlaw Sylver and pursued by the stoat Sheriff Falshed, journey to a far-away city where they find themselves entangled in a battle between rivalling clans of squirrels. Published in Germany under the title "Belagert die Sturmburg."