The narrator informs us that we're starting with Helen's letters to her sister, Meg.
The first letter describes a house – a nice, homey place surrounded by trees. Sounds pretty good to us.
Helen's apparently there, visiting some wealthy friends: Mr. and Mrs. Wilcox and their children. She plans to return to London that Saturday, where Margaret is detained at home with their feeble brother, Tibby. Helen claims that vigorous men like Mr. Wilcox and his son, Charles, would be a good influence on Tibby.
Helen describes the Wilcoxes, who sound like a nice family, albeit somewhat batty. They all love the outdoors, and occupy themselves there, despite their hay fever. The family is composed of Mrs. Wilcox, Mr. Wilcox, and three children, Charles, Evie, and the yet-to-arrive Paul.
Helen's second letter reveals that she's been won over completely by the Wilcoxes – they're apparently totally different from the liberal, wacky Schlegels, and she's intrigued by this glimpse into their lifestyle. For once, Helen (who seems like quite an opinionated young lady) is "knocked into pieces" in conversation by Mr. Wilcox, and she enjoys it.
Helen's third letter is short and dramatic – she is in love with Paul Wilcox.