Novel: Quicksand
Passage: That was the crux of the whole matter.
For Helga, it accounted for everything, her
failure here in Naxos, her former loneliness in
Nashville. It even accounted for her engagement to James.
Definition: an essential point requiring resolution or resolving an outcome
http://www.merriam-webster.com/dictionary/crux
Understanding: This is when Helga realizes that she will not be able to solve he engagement issue. It is a problem that needs a resolution. Therefore it is a crux.
