The following version of this book was used to create this study guide: Mootoo, Shani. Cereus Blooms at Night. Grove Press, 1998. 3rd printing.

We are introduced to the character of Mala Ramchandin by Nurse Tyler, the story's narrator. The novel begins with Mala's admission to the Paradise Alms House, where Tyler has just recently started to work as the only male nurse in residence. Because of the rumors and scandal that have surrounded Mala her whole life, and the recent murder charges brought against her--thrown out of court by local judge Walter Bissey--the other nurses are too wary to approach Mala, and Tyler is assigned to be her caregiver. While looking after Mala, Tyler begins to uncover the what has happened to lead to her descent into apparent madness. Tyler, who was trained abroad in the Shivering Northern Wetlands, is seen as an outsider; his sartorial choices, his effeminacy, and his sexuality set him apart from his peers. Tyler thus empathizes with Mala, sensing that she has been misunderstood and underestimated. He takes on the job of recording her story to reveal the truth.

What follows is a series of interwoven episodes that appear to have been collated by Tyler. These chapters are told in the third person, past tense, from the perspective of a narrator with limited omniscience. They recount the coming of age story of Chandin Ramchandin, Mala's abusive father; the story of Pohpoh, Mala's younger self; her sister Asha; and Pohpoh's childhood friend Boyie, later known as Ambrose; and the story of his son Otoh. Tyler's record outlines how each of these stories intersect and lead to the scandal up on Hill Side which brings Mala into his care. With each new episode, Tyler adds another piece to the puzzle that makes up Mala's history, while describing back in the present his growing relationship with Otoh, and Mala's steady improvement under his care.

As a child, Chandin Ramchandin is adopted by the Reverend Thoroughly and his wife with the goal of ingratiating the Thoroughlys to the Indian population of Paradise, Lantanacamara. With Chandin's Christian conversion, the Thoroughlys strengthen their bond with the colonized people, and Chandin is given a top notch education in exchange. While living with the Thoroughlys and adopting their ways, Chandin finds himself falling in love with his adoptive sister, Lavinia Thoroughly, whose only attentions are bestowed upon her best friend Sarah, an Indian girl from school. As Chandin's affections grow, it becomes clear that Lavinia has no interest in him, and one day, the Reverend explicitly forbids Chandin from harbouring these "impure" feelings for his adoptive sister, stressing that Chandin must think of himself as family, and that his attachment is immoral. Chandin resolves to keep his feelings hidden. Not long after, the Reverend announces that he is taking the family on a trip back home to the Shivering Northern Wetlands, but Chandin is not invited. When he confesses his love to his adoptive sister, Chandin is rejected, and his feelings for Lavinia begin to sour into self-loathing. News arrives that she has become engaged to a Wetlandish cousin, and Chandin marries Lavinia's childhood friend Sarah out of spite.

Sarah and Chandin have two children and a sad, loveless marriage. Lavinia returns to Paradise, having broken off her engagement, and rekindles her relationship with Sarah. Chandin becomes increasingly jealous of Lavinia's closeness with Sarah and her love of the children. Chandin's eldest daughter Pohpoh soon realizes that her mother Sarah and her Auntie Lavinia are lovers and, when Chandin begins to realize what has been going on under his nose all along, the two women plan their escape from the island with the children. The day of their departure, Pohpoh runs back to the house to retrieve a forgotten clipping from the cereus plant that Lavinia once transplanted for her and Asha, just as Chandin returns home to find them trying to flee. In the chaos, Sarah and Lavinia leave without Pohpoh and Asha--who refuses to be separated from her sister--abandoning the girls to the wrath of their father.

In his rage and paranoia, Chandin insists that his daughters sleep on either side of him for the first few nights after the abandonment, to assure that he will not be left again. One night, Chandin rapes Pohpoh, and from then on, his daughters learn that one of them is expected to spend the night in his bed being raped. Pohpoh tries her best to protect her sister Asha, and begins to go in her sister's place whenever Asha is called for, knowing that their father is too drunk to ever spot the difference.

At school, Pohpoh is picked on by Walter Bissey, a schoolyard bully who torments insects and snails with his gang of friends. Pohpoh nurses a crush for Walter despite his harsh treatment of her. As someone who is pitied and ostracized by the rest of the town, Pohpoh wants nothing more than for him and his friends to like her and for them to play together. Boyie is Pohpoh's only true friend, yet he is often cowardly and shy, unable to help Pohpoh in moments of adversity. Pohpoh leads Boyie in the schoolyard on snail-saving missions, and one day, the two share an intimate moment in his bedroom, with Pohpoh calling the shots and leaving Boyie as soon as she feels sexually satisfied.

The reader is brought years later to Boyie, now called Ambrose, in his prime when he is given a theology scholarship in the Wetlands. His childhood experiences with Pohpoh have cleft him with a lifelong fascination for insects, and he returns to Paradise as a trained entomologist, full of ideas about insects, theology, and language, and about the possibilities afforded by the natural world. He shares his ideas with Pohpoh (now called Mala) and begins to court her, with dreams of sharing a life together one day. As Mala and Ambrose's romance begins to flourish, so do Mala's feelings of guilt and worry that one day her father will find out about the whole affair. On the day that Ambrose and Mala finally consummate their love, Chandin feels a pain in his chest and comes home early to see Ambrose leaving out the back of their house. He rapes Mala more brutally than ever as punishment for her 'betrayal,' sexually assaulting her several times throughout the night and leaving her battered and bruised for Ambrose to find the next morning. When Ambrose returns and discovers what has been happening all along to Mala, Chandin attacks his daughter's lover and Mala fights back. In the scuffle, Chandin falls to the ground and is stunned when hit on the head by a swinging door. Ambrose runs away from the Ramchandin house in fear and shame, and Mala takes it upon herself to slam the door repeatedly on her father's head until he is quite lifeless. She drags his body into the basement room of the house and locks the door on him, building a barricade of furniture between herself and the room beneath. Later, the police determine that Chandin was likely kept alive for some time in this room before finally expiring.

Back in the present day at the nursing home, Mala is visited by Ambrose, who is now elderly and has a grown-up son of his own named Otoh. Tyler takes to the beautiful Otoh right away, and Otoh begins to recount his own interactions with Mala in recent years along with the story of his parents, with his account added to Tyler's collection of flashback narratives.

Years earlier, Ambrose, riddled with guilt about his inaction on the day of Chandin's attack, and cursing himself for being once more unable to help Mala in a moment of need, takes to sleeping through life, resolving to provide for Mala through monthly parcels. His wife Elsie resents Ambrose's continued obsession with that old "Bird" up on the hill, yet she dutifully adds to the parcels every month. Otoh begins to deliver them himself, and his curiosity around Mala grows and grows. One day, he dresses in his father's old clothes, carrying along a repaired gramophone that Ambrose had gifted Mala right before her father discovered them (and which Ambrose retrieved from Mala's house a few days after the incident, when it seemed like Mala had gone mad and could not recognize Ambrose any longer). The elderly Mala mistakes Otoh for Ambrose and leads him into the house, down to the basement, showing him why her father can no longer hurt them. In a panic, Otoh flees Mala's house and nearly passes out on the street, feverishly telling the townspeople about the decaying body he has seen at Mala's house. The police arrive and, under the pretence of looking out for Mala's safety, they insist that she show them inside. She unlocks the doors and lead the police down to her father's body. They plan to return the next day to gather evidence for a case against Mala for his murder.

Through flashbacks told from Mala's perspective, sitting in her garden as Otoh first approaches, the reader becomes privy to one of Pohpoh's nighttime excursions--a regular coping mechanism that allows her to leave the oppressive confines of her father's violent household, to explore the neighbourhood under cover of darkness, entering homes of her neighbours, homes that host families that are happy and safe, undetected. Pohpoh's childhood experience, and the moment when the police arrive in Mala's garden, become braided together. Mala lets herself travel back to young Pohpoh, protecting her in her mind, and Pohpoh is in turn brought back into the present, visible to Mala alone as she descends into the house, showing not only the police officers the dead body, but Pohpoh, assuring her young self of their safety. Mala tells Pohpoh to fly, to escape the house and yard, and in Mala's mind's eye, Pohpoh takes off from the garden, flying away from the police, from her father, from all cruelty and harm, and circling high above Paradise until all is out of sight.

The night after the police arrive, Otoh decides to burn down Mala's house, destroying all evidence of her father's death, and leaving a dark cloud over all of Paradise. The novel concludes with a visit to Mala at the alms house from Judge Walter Bissey, who brings with him a series of undelivered letters from Asha, who had run away during her teens. She writes of having found work and happiness in the Wetlands only to finally settle in Canada. As the characters wait for the cereus plant to blossom, Tyler and Otoh confirm their love for one another, and Ambrose and Mala find a new sort of peace. They are left awaiting more news from Asha, or maybe even a visit, and the promise of the sweet and fortifying blossoming of the cereus.

• Note: Chapters are not numbered in Cereus Blooms at Night, but the novel is divided into sections that are separated by little illustrations of insects, drawn by the author. This study guide numbers these as chapters, eg: Section 3, Chapter 2 refers to what follows the second insect illustration found in Part III.