Nothing much happens in the village of Foxglove, or so junior archivist Sylvester Lemmington thought until the day he and his girlfriend Viola pull a wounded wayfarer from the river. Before this unfortunate wayfarer expires, he presses upon Sylvester a piece of paper, which Sylvester will soon discover is part of a map to the legendary loot of Cap'n Josiah Adamite. Soon there is another new arrival in Foxglove, Cap'n Terrigan Rustbane, the cruelest buccaneer in Sagaria; and he wants his map back.

Before long, Sylvester, Viola and, embarrassingly, Viola's mum are carried away aboard Rustbane's pirate ship in search of treasure - facing cannibals, carnivores and a cutthroat crew. Can Sylvester save Viola, her frighteningly gritty mum, find his long-lost father, rescue Foxglove from the murderous rule of its mayor, and discover true happiness? It's a tall order. But then Sylvester is a librarian. And a lemming.