The story begins with the narrator and his friend Skinny Dillon scaring 'Lisha, a college-educated African-American who resents doing menial labor. They trick 'Lisha into believing in the power of Obeah by disguising themselves and creating supernatural sounds. This prank deeply affects 'Lisha, who becomes obsessed with Obeah and starts spreading tales among the local African-American community.

'Lisha's newfound belief in Obeah coincides with the arrival of a mysterious European named Lopez da Vasca and his two servants, Santiago and Jose, in the town. 'Lisha quits his job and becomes increasingly erratic, speaking of a coming event and attracting a following among the African-Americans.

The narrator and Skinny decide to follow 'Lisha to uncover what he is up to. They discover that 'Lisha and his followers are meeting in the Haunted Brakes, a notorious and feared area among the locals due to its history of supernatural occurrences. There, they witness 'Lisha delivering passionate speeches about Obeah and a forthcoming liberator who will lead them to freedom.

The boys observe that da Vasca and his servants are involved in the gatherings. One night, they encounter Santiago and Jose at a secret meeting in the cane brakes, where they learn about a planned uprising among the African-Americans, instigated by da Vasca.

As the tension in the town rises, a gruesome murder occurs: an old maid, Miss Kenson, is found beheaded in her home. The narrator is initially suspected but is eventually exonerated. Da Vasca, posing as a detective, manipulates the investigation, trying to incriminate the narrator. However, the narrator realizes that da Vasca and his men are behind the murder and other sinister activities.

With the help of Lin Landers, a young attorney, and Berwick, a mysterious Englishman, the narrator uncovers the true identity of da Vasca. He is a mulatto criminal from Haiti, skilled in Obeah and intent on stealing a valuable diamond hidden in the Haunted Brakes.

The story reaches its climax when the narrator, Skinny, and the others confront da Vasca and his men in the Haunted Brakes. After a fierce struggle, Santiago is killed, but da Vasca escapes on a hidden launch, evading capture. The narrator and his friends manage to stop the uprising and recover the stolen diamond, bringing a semblance of peace back to the town.