This is the penultimate full Swallows and Amazons novel by Arthur Ransome, and revolves around Nancy, Peggy, Dick and Dorothea. The Swallows do not appear at all, although they are mentioned frequently (it also is evident that they are about to visit at the end, presumably a set up for the next book).
Nancy and Peggys' great aunt has been mentioned in at least one previous book, but has not been given much to do before this title. Here, she invites herself to babysit for the Amazon girls while their mother is away. However, Nancy and Peggy are none too pleased, partly because they had Dick and Dorothea visiting, and also because their aunt insists that they wear frocks, which does not meet the approval of the girls, both tomboys who like to pretend they are pirates. The aunt also calls them Ruth (Nancy's real name, mentioned briefly in the very first book), and Margaret.
So, Nancy and Peggy hide Dick and Dorothea out in "The Dog's Home" nearby to stop the great aunt discovering them, and have to keep sneaking out to spend time with them. Nancy and Peggy are the martyrs of the title, having to yield to everything their great aunt wants, while Dick and Dorothea are the picts.
There is another recurring character, "Squashy Hat" from "Pigeon Post", now known by his real name of Timothy (I never really good a good idea as to his age; I always pictured him as a middle aged or older man, though I could be very wrong). He gets more to do towards the end of the book.
Overall, I enjoyed this more than the previous two titles; I managed not to miss the Swallows, mostly because of Nancy and Peggy (I love Nancy's catchphrase, "Jibbooms and bobstays", which she uses frequently). The book ended up taking a turn that I didn't expect at all towards the end, and my opinion of the great aunt definitely changed between the start and the end of the book.
I hope to read the last full Swallows and Amazons book, "Great Northern?", soon.
Next book: The Hiding Place (Robert Shaw)