The novel tells the story of Geoffrey Firmin, an alcoholic British consul in the Mexican city of Quauhnahuac, on the Day of the Dead in November 1938.

[11] Asals notes that the important 1944 revision evidences Lowry and Bonner paying extraordinary attention to references to fire in the novel, especially in Yvonne's dream before her death.

[13] Lowry's lengthy reply, dated 2 January 1946, was a passionate defence of the book in which he sensed he had created a work of lasting greatness: "Whether it sells or not seems to me either way a risk.

The letter includes a detailed summary of the book's key themes and how the author intended each of the 12 chapters to work;[14] in the end, Cape published the novel without further revision.

Under the Volcano and Ultramarine were both out of print by the time Lowry died of alcoholism (and possibly sleeping pills) in 1957,[15] but the novel has since made a comeback.

[18] In the first chapter, set on 2 November 1939, Jacques Laruelle and Dr. Vigil drink anisette at the Hotel Casino de la Selva, on a hill above Quauhnahuac (an approximation of the Nahuatl name of Cuernavaca), and reminisce on the Consul's presence, exactly a year ago.

Laruelle is scheduled to leave Quauhnahuac the next day, but has not yet packed and does not want to go home, spending his time instead at the Cervecería XX, a bar connected to the local cinema, run by Sr. Bustamente.

Playing a variation on Sortes virgilianae, his eyes fall on the closing words of the chorus in Marlowe's Doctor Faustus, "Cut is the branch that might have grown full straight...", then finds a desperate letter by the Consul to Yvonne, a final plea for her to return, interspersed with descriptions of alcoholic stupor and delirium tremens.

Chapter 2 finds the Consul sitting at the bar of the Bella Vista hotel in Quauhnahuac at 7:00am on 2 November 1938, drinking whisky the morning after the Red Cross ball, when Yvonne enters.

Throughout the chapter, hallucinations, memories, and imaginary conversations interrupt his train of thought, and he hears voices that alternately tell him all is lost and that there is still hope.

While Yvonne is in the bathroom, however, he leaves the house to visit a cantina but falls facedown in the street, passed out, and is almost run over by an English driver in an MG Magna who offers him Burke's whisky from a flask.

Vigil (also hungover from the Red Cross ball) visits Quincey; he carries a newspaper with headlines of the Battle of the Ebro and the sickness of Pope Pius XI.

Hugh and Yvonne return, and the Consul wakes up from a black-out in the bathroom, slowly remembering the strained conversation during which it is decided that rather than accept Vigil's offer of a day trip to Guanajuato they will go to Tomalin, near Parian.

It is revealed that Hugh's signing aboard the S.S. Philoctetes was intended as a publicity stunt to promote his songs, which are to be printed by a Jewish publisher named Bolowski.

The four arrive at Jacques Laruelle's home, which features two towers that the Consul compares to both Gothic battlements and the camouflaged smokestacks of the Samaritan.

The Consul still has more time to waste, so he stumbles into the Terminal Cantina El Bosque, wherein he chats with the proprietor, Senora Gregorio, and has at least two more drinks.

Hugh believes the term to mean "a shoeless illiterate" but the Consul corrects him, claiming that pelados are "indeed 'peeled ones,' the stripped, but also those who did not have to be rich to prey on the really poor".

This chapter offers Yvonne's point of view, including her memories of the Indian that had been injured and the emotion that she feels when reflecting on the volcano, Popocatépetl.

As the chapter continues, she reminisces about her childhood and early adulthood in multiple instances; for example, when she claimed to see her father come toward her in a hallucination, when she thinks about her mother's death around the time of World War I, and when she discusses her life as an actress in Hollywood.

Various landmarks, including the San Francisco Convent, the City Parish and the Tlaxcala Royal Chapel and Sanctuary, are mentioned as the Consul reads a tourist information booklet and remembers places he and Yvonne visited in happier times of their past.

Yvonne is trampled by the horse with the number 7 branded on its leg and imagines seeing her dream house in Canada burn down as she dies.

[26] Lowry alludes to Goethe's Faust as well and uses a quote for one of his three epigraphs but Marlowe's dominates, with the Consul being suggested as a Faustian black magician by Hugh.

The Consul "often associates himself with Faustus as a suffering soul who cannot ask for salvation, or who even runs toward hell", and parodies Marlowe's line about Helen of Troy ("was this the face that launched a thousand ships, / and burnt the topless towers of Illium?

"[28] A literary game based on the Sortes virgilianae—a form of divination by bibliomancy in which advice or predictions of the future are sought by randomly selecting a passage from Virgil's Aeneid, but with Shakespeare replacing Virgil—is an important theme.

"[36] Michael Hofmann, who would edit the collection of posthumous work of Lowry's The Voyage That Never Ends, wrote, "Under the Volcano eats light like a black hole.

I left thinking it one of the greatest novels of the 20th century... Lowry is closer to Melville and Conrad than Joyce, but he creates his corner of Mexico in a manner similar to the Dublin of Ulysses: not by describing it so much as by building an alternate reality from language.

"[39] Novelist Elizabeth Lowry (no relation), writing in the London Review of Books, described it as a "black masterpiece about the horrors of alcoholic disintegration.

"[40] Reviewing Gordon Bowker's biography of Lowry, The New York Times commented on Volcano's legacy: "Under the Volcano is too famous to be just a cult object, but more than most great novels it is revisited year after year by a few zealous defenders, who place Lowry high up in the modernist pantheon, while the rest of the world is only barely aware of his masterpiece as an exotic and harrowing read.

[2] John Huston directed the 1984 film adaptation, with Albert Finney, Jacqueline Bisset, Anthony Andrews and Katy Jurado.

Selections from Lowry's novel are read by Richard Burton amid images shot in Mexico, the United States, Canada and England.