Black Dogs is a fictional memoir of two people who are very much in love, yet complete opposites of one another. June and Bernard Tremaine's story is told by their son-in-law, Jeremy, forty-three years after the pivotal events of their honeymoon, which caused this young couple to live apart from each other for the remainder of their days.

Young, idealistic, and naïve British communists, June and Bernard join the Party the same week they get married. They had waited until after the end of World War II to do both things, and their future plans are to spend their lives in the pursuit of an idealistic, communist utopia on earth through their involvement with the practical politics of socialism Both come from the British upper class and are cultured, educated, and polished, but have little experience getting their hands dirty in life.

Their honeymoon takes them across war-torn Europe, and the couple sees the war's devastation first hand for the first time in their sheltered lives. A confirmed atheist, Bernard reacts with hopelessness and despair, taking refuge in idealistic political platitudes. Along the way, June has a terrifying encounter with two vicious black dogs, which become the instrument of her conversion to belief in God. This day marked the beginning of the end for the two loving souls, who were always to remain married and in love, but forever to live apart, carrying on their argument as to the existence of God even beyond the grave. It is up to the narrator, Jeremy, to sort their story out and heal the longstanding rift in his family.