The novel is set in Dublin during the week leading up to the Easter Rising of 1916. All the characters are members of a complexly interrelated Anglo-Irish family. As the story begins Andrew Chase-White is a young Second lieutenant in King Edward's Horse, spending a leave with his family in Ireland before accompanying his regiment to France.^[2]: 13

Andrew Chase-White grew up in England, the only child of Protestant Anglo-Irish parents. His recently widowed mother Hilda has decided to move to Ireland. Andrew's paternal grandfather was his grandmother's second husband. With her first husband she had two children, Brian and Millicent Dumay. Millicent married Sir Arthur Kinnard and inherited his property when he died young. Brian, who converted to Catholicism as a young man, married Arthur Kinnard's sister Kathleen, who also converted. They had two sons, Pat (Andrew's contemporary) and his younger brother Cathal Dumay, both ardent supporters of independence for Ireland. After Brian's death Kathleen married Andrew's Roman Catholic uncle Barnabas Drumm, Hilda's brother. A third Kinnard sibling, Heather, married Christopher Bellman and died young. Christopher's only child is Frances, whom Andrew has known all his life and plans to marry.^[2]: 19

When Andrew and Frances visit Kathleen, Pat and Cathal in their house in Dublin, Andrew is goaded into taunting Pat with his failure to enlist in the British Army. The following day Andrew, Hilda, and Christopher call on Millicent in her Dublin house. Unknown to his family, Christopher is in love with Millie, whom he has been helping financially for several years, and has been trying to convince her to marry him. This is complicated by the fact that Frances dislikes Millie, but he is encouraged by the expectation that Andrew and Frances will soon marry. Millie promises to come to Christopher's house later in the week to give him her answer.^[2]: 84

Pat's stepfather Barnabas Drumm is another of Millie's admirers. Years before, his passion for Millie had led to his leaving the seminary where he was training for the priesthood. His marriage to Kathleen proving unhappy, he reconnected with Millie and became a frequent visitor at her house, where he has the status of a tolerated relation. When Millie goes to Christopher's house to tell him she will accept his marriage proposal, their conversation is overheard by Barnabas.^[2]: 145

Millie has allowed her cellar to be used as an arms depository by the Irish Volunteers. Pat Dumay, an officer in the organization, has been informed that an armed insurrection is planned for Easter Sunday, and comes to inspect the weapons. He encounters Millie, who informs him that she is in love with him and invites him to Rathblane, her country house in the Wicklow Mountains. Shocked, he runs away.^[2]: 182

Andrew asks Frances to marry him, and is surprised and devastated when she refuses. Later he goes to Rathblane and confides in Millie that he is not engaged to Frances and that he is a virgin. Millie kisses him and offers to initiate him sexually, but he refuses her offer and leaves.^[2]: 192

Pat and Cathal are bitterly disappointed on Saturday, when the insurrection in cancelled. In despair, Pat goes to Rathblane on Saturday night, and finds that Millie is already in bed with Andrew. He rushes out of the house, just as Christopher is arriving unexpectedly. Millie tells Christopher that she will not marry him after all, and that she has seduced Andrew and is in love with Pat.^[2]: 251

On Monday morning Andrew goes to Pat's house, unaware of the rising rescheduled for that day. Pat takes him prisoner and leaves him handcuffed to Cathal in order to keep Cathal out of the fighting. They are freed just as the insurrection is starting and the novel ends with Andrew and Cathal observing the beginning of the rising in front of the General Post Office. An epilogue set in 1938 briefly describes the later lives and deaths of several of the protagonists.^[2]: 308

The Red and the Green is the only historical novel by Iris Murdoch.^[3]: 140 Murdoch, though born in Dublin to Protestant parents, left Ireland as an infant and spent her life in England. She undertook extensive research into Irish history in preparation for writing the novel.^[4] There is considerable debate and discussion about Irish history and nationalist politics throughout the novel, chiefly carried on by Christopher Bellman and Pat and Cathal Dumay.^[3]: 141 Murdoch does not show an obvious political bias, but the book leans toward "the liberal Irish patriotism of the Anglo-Irish".^[5]: 13

Incest is an important theme in the novel, and a common topic in Murdoch's fiction, in which a "quasi-incestuous competition of members of one family for a single beloved is ubiquitous" as are actual incestuous relationships.^[5]: 105 The baffling complexity of Andrew's family, a source of pride for his mother, is characterized by Millie as "practically incestuous".^[2]: 18 Besides going to bed with Andrew, who calls her "Aunt Millie", and trying to seduce her nephew Pat, she claims to have had a sexual relationship with her half brother, Andrew's father.^[3]: 142

Sexual initiation is one of the themes of the novel.^[3]: 140 Both Pat and Andrew are virgins who feel "a fear of sex and a fixation on long-suffering mothers", which the critic Declan Kiberd notes is a "complex of attitudes which was by the 1960s being recognized as a pathology".^[6]

The novel has been characterized as part of Murdoch's "romantic phase" in which she was concerned with "the responsibilities, impositions and ties of marriage, or, in the case of The Red and the Green, of religious vocation".^[7] In this case Barnabas Drumm, while pining for Millie and resenting his virtuous wife Kathleen, is unable to give up his dream of a religious calling, and feels himself to be "by vocation a failed priest".^[2]: 113 Several chapters are devoted to Barney's religious crises, in which he wrestles with his feelings of guilt and ineffectually resolves to redeem himself.^[4]

The Red and the Green was widely reviewed in Ireland, Great Britain, the United States and elsewhere.^{[8]: 546–561} The reviews were mixed, with several critics finding that the "bedroom farce aspect" centred on Millie was "fatal to the book".^[4] Christopher Ricks wrote in the New Statesman that Murdoch's attempt to "combine a flatly faithful account of what happened in Dublin in 1916 with a love-imbroglio" showed "honourable and gigantic ambition" but resulted in a failed novel in which the "sexual permutation game both withers and demeans Irish history". Ricks argued that her "clockwork" characters and contrived plot resulted in fiction that failed to live up to the demands of her own theories of literature.^[9]

In the New York Times, John Bowen also characterized The Red and the Green as a "mechanical novel" in which "contrivance is piled on contrivance", in a manner unworthy of "a novelist of this stature".^[10] Another New York Times reviewer disagreed, calling The Red and the Green a "brilliant and entertaining" novel with a "magnificently wayward heroine" in Millie Kinnard and a "style that somehow blends the methods of Sartre and Stendhal".^[11] The Time reviewer was unimpressed by the novel, calling it "neither her best book nor her worst". The review praised her descriptive writing but called her characters "sexually confused, tortured by unexplained feelings of guilt, and totally ineffectual and unbelievable as human beings".^[12]

Murdoch's biographer Peter J. Conradi notes that the Irish reviews were "generally good", including one by Seán Ó Faoláin in the Irish Times.^[13]: 464 Benedict Kiely recommended it to American readers as a guidebook to "the English and the Irish" characters and praised Murdoch's ability to discriminate, "with scholastic precision ... between English rain and Irish rain".^[14]