The Heart of the Matter is a novel by Graham Greene, published in 1948. It deals with Catholicism and the moral decay of the protoganist, Scobie.

Scobie is a policeman at an British colonial town on the West Coast of Africa during the Second World War. He is a deeply unhappy person, living in an empty and loveless marriage with his wife of 15 years, Louise, a Catholic. For her sake he had himself converted to Catholicism, but is now rather superficial in the practice of his faith.

In an effort to free both of them from this unsatisfactory situation, Louise goes to South Africa, leaving Scobie behind. Shortly afterwards, the policeman meets a young Englishwoman called Helen, a survivor from a shipwreck, and starts a passionate affair with her, all the time being aware that he is committing a grave sin - adultery. When Louise unexpectedly returns, Scobie struggles to keep her ignorant of his love affair. But he is unable to renounce Helen, even in the confessional, so the priest tells him to think it over again and postpones absolution . Still, in order to please his wife, Scobie goes to mass with her and thus receives communion in state of "mortal sin" - one of the gravest sins for a Catholic to commit.

Now desperate, he decides to free everyone from himself - even God - so he commits suicide, being aware that this would end in sure damnation according to the teaching of the Church. But his efforts prove useless in the end - Louise had been not as naive as he had believed, the affair with Helen and the suicide are found out, and his wife is left behind wondering about the mercy and forgiveness of God.