In this novel Lively relates the rippling consequences of a a single event. That event is the mugging of retired teacher Charlotte Rainsford, 77 years old. Charlotte's hip is injured, requiring her to live with her daughter and son-in-law for several months. This means her daughter has to work less, especially at first, causing ripples in the extended family of her employer too.
On it goes, like a series of concentric circles or Matryoshka dolls. No spoilers here, because you should read the book.
While some critics find some links in the chain to be implausible, for me every connection is fully believeable and realized. Even lively, you might say.