In Trinidad, a local legend claims that those who eat the cascadura fish will always remain on the island. The cascadura, a small fish found in muddy streams, makes a delicious dish, but few tourists know about it because Trinidadians don't advertise it. This story is connected to this legend, but the narrator Sam, the supervisor of the estate owned by Franklin, is unsure of the belief and states that he has seen and heard enough strange things to be cautious about the supernatural.
An Englishman named Johnson came to Trinidad for a holiday on his friend Franklin's estate. Franklin, the owner of a cocoa plantation, treated his workers well and was respected by the villagers. Johnson, interested in superstition and witchcraft, spent his days exploring the estate and listening to local stories. He learned about Papa Bois, a forest spirit, soucouyants that suck blood, and balls of fire that frighten people.
One evening, Franklin claimed to have seen a ball of fire while riding his horse, but couldn't explain it. Johnson, skeptical, didn't believe in these stories, but Franklin insisted on their reality. Johnson was particularly interested in soucouyants. He asked Chanko, the old watchman, about his encounters with these creatures. Chanko told him about a terrifying experience where he saw a ball of fire approaching him, but managed to ward it off using the sign of the cross. Johnson, eager to document these tales, wrote them down in his notebook.
However, a rumor started spreading about Johnson and Urmilla, a beautiful Indian girl who worked on the estate. Urmilla had defied her father's attempts to marry her off to a wealthy merchant. Her father sent her to work in the estate in order to keep her under the watchful eyes of Franklin, the estate owner. Johnson, a young man, and Urmilla, a beautiful woman, were often seen together. The narrator, worried about the consequences of their relationship, tried to find out more from Franklin, but he remained silent.
The narrator was concerned about the possible repercussions for Urmilla if their relationship became known. He knew that the villagers would be upset, and Urmilla's father, Sookdeo, would be furious. He decided to wait and see what happened, hoping that the rumor would simply fade away.
Sam, the narrator, got his suspicions confirmed when he witnessed the lovers - Johnson and Urmilla- kissing by the river. Franklin, the plantation owner, was also aware of the rumors and asked Sam to stop the gossip.
Sam later finds out that Johnson climbed an immortelle tree looking for a corbeau's egg, a lucky charm, and gets stuck. He asks Urmilla for help and Urmilla seeks the help of Sam and he is surprised to see that Urmilla calls the Englishman by his first name ‘Garry’ which fuels Sam's jealousy. Sam tells Johnson about Urmilla's past and learns that Johnson loves her. This revelation stirs up Sam's old feelings for Urmilla and he realises he still cares for her.
The next day, Sookdeo, Urmilla's father, comes to ask Franklin to be the godfather at his granddaughter's christening. Sam is disappointed, hoping Sookdeo had come to speak about Johnson and Urmilla. Sookdeo confronts Franklin about his concerns regarding Urmilla and Johnson’s relationship. Franklin, knowing the truth about their connection, lies to Sookdeo. Meanwhile, the narrator, Sam, struggles with his own feelings for Urmilla and his resentment towards Johnson. He contemplates Johnson's motivations and questions his right to disrupt his life. Sam tries to avoid Urmilla and the Englishmen, but he eventually finds himself drawn back into their lives. Johnson announces his departure, stating he will not take Urmilla back to England. Sam, feeling torn and conflicted, tries to rationalize Johnson’s actions.
Despite Johnson’s departure, Urmilla remains emotionally attached to him. She sends a dish of cascadura to Johnson through Sam, hoping it will bring him back. Sam, now drunk, facilitates Johnson's meeting with Urmilla before he departs. He arranges for village women to perform Indian dances to cover for Johnson's absence. After Johnson leaves, time passes slowly in the valley. Sam tries to pursue Urmilla, but she remains preoccupied with Johnson and constantly inquires about his whereabouts and potential return.
Urmilla believed that Garry would return to Trinidad because he had eaten a "cascadoo," a fish curry which is believed to bring people back to the island. Sam tried to convince Urmilla to move on, but she refused. Over time, Urmilla’s father became ill, and before his death, he asked her to marry Sam. Although Sam said he would only marry her if she truly wanted him, Urmilla agreed. But just before the wedding, a letter arrived from Garry. He was ill and wanted to return to Trinidad. Sam was heartbroken and told Urmilla he wouldn’t hold her to her promise. He then decided to leave Trinidad.
Sam had always wanted to leave the island, and now he was finally doing it. He left with the understanding that Garry would help out with the estate until Franklin found a replacement. Before leaving, Sam saw Garry and was surprised to learn that Garry was going to marry Urmilla. He was even more surprised when Garry asked why Sam didn’t marry Urmilla himself. Garry told Sam that he could not change Urmilla’s belief that it was the cascadoo that had brought him back to Trinidad. Sam left the island knowing that Urmilla was approaching the local obeah-man for a medicine to cure Garry's illness.