Betrayal and lying aren't necessarily the same thing. Lying often comes after a betrayal in an effort to cover it up. As the old nursery rhyme goes, first comes betrayal, then comes lying, then comes pushing a baby that isn't your husband's in a baby carriage. That's almost exactly where we are in The Girl on the Train opens. Within the last year, Rachel's husband has had an affair, divorced her, married his mistress, and had a baby. Good times. Even though it happens before the book begins, this epic betrayal sets the tone for the whole novel.
Questions About Betrayal
Why is Rachel so offended when she sees "Jess" kissing another man?
What Rachel tells Scott is mostly the truth—she only lies about how she knows Megan. Why does Scott feel so betrayed when he discovers Rachel didn't tell the whole truth?
Does Scott overact when Megan tells him she has been having an affair?
How was Megan betrayed as a teenager, and how does this betrayal affect her for her entire life?
Chew on This
An imaginary betrayal—Rachel's imaginary "Jess" having an affair—is what begins Rachel's story in this book.
You can follow the timeline back all the way to Rachel marrying Tom. If he hadn't ever betrayed her, the events of the book wouldn't ever happen.