What's a summary of The Heart of the Matter?

Graham Greene’s novel explores the moral dilemmas of a middle-aged, married, Catholic, British, man when he falls in love with and has an affair with a much younger woman. Working as a colonial police officer in Sierra Leone (part of British West Africa), Major Scobie meets Helen Roit while his wife, Louise, is traveling abroad. Although he had long ago admitted to himself that their marriage had reached an impasse, Scobie is unwilling to abandon Louise, whom he feels is totally dependent on him. Furthermore, for him as a Catholic, divorce is unthinkable, but continuing to live a lie adds several kinds of torment, including his inability to confess to his sin.
The novel takes place during World War II, when the colony’s Atlantic coastal location was strategically important. Scobie’s situation becomes professionally complicated as well because he owes money to a Syrian merchant of dubious reputation, which opens him up to blackmail as he may inadvertently have involved himself in helping the merchant smuggle goods to the Nazis. Helen is not a realistic match for Scobie because she does not understand faith; age is not the real issue in that, although she is only 19, she has already been made a widow through the shipwreck that brought her to Africa and into Scobie’s life. She privileges their love over Scobie’s religious scruples. Deciding to switch one sin for another and risk his soul in doing so, Scobie decides to take his own life. He does so by faking a heart attack, hoping to fool the doctor so he will not be diagnosed as a suicide, thus trying to exploit what he imagines as a theological loophole.