Swallowdale is the second novel in the Swallows and Amazons series that follows the adventures of Walker siblings (Swallows) and Blackett sisters (Amazons). Returning to Wild Cat Island for their second summer holiday by the Lake, the Swallows find the Amazons suffering from strict discipline enforced by their Great Aunt Maria who is a stickler for "proper" behavior, demanding that the Amazon pirates act like "young ladies." Despite this, Nancy and Peggy escape the Great Aunt and arrange a rendezvous, but on the way the boat hits Pike Rock and sinks. All are saved, but camping on the Wild Cat Island is impossible. An alternative appears to replace camping, as Roger and Titty find a beautiful hidden valley, Swallowdale, up on the moors above the lake. The Swallows discover a secret cave in Swallowdale,
a trout tarn, the "knickerbockerbreaker", and enjoy new adventures of lakeland life.