The Film: Aaand... another film about a bored and isolated woman, trapped in a mundane existence, seeking a little excitement. 

Kate Winslet's Sarah is an academic, unhappy in the role of housewife and mother. She has too much intellect for her own good.

The Affair: Underappreciated Sarah buys a raunchy red bathing suit and seduces spunky dad Brad (Patrick Wilson), who's also married.

They tug on that thread and just keep on pulling.

Long-Term Relationship? They get their come-uppance, and then some. The guilt'll surely wash away any lasting loving feelings.