“Her expression was curiously familiar - it was an expression I had after seen onwomen’s faces, but on Myrtle Wilson’s face face it seemed purposeless andinexplicable until I realized that her eyes,wide with jealous terror, were fixed not onTom, but on Jordan Baker, whom she took to be his wife.” (pg 124-125)
This is an example of foreshadowing. Fitzgerald uses this in this sentence to showhow everything that has been built up in the novel to this point and all in the matterof a few pages it completely crumbles and decays into the crushing reality of thismorally corrupt time period.