Jesse was Theo’s uncle. Joe Putnam explained that Jesse struggled with his sexuality and that, as a kid, their father caught Jesse wearing one of their mothers dresses and "beat him black and blue." He was possessed by Apophis, Devouring Worm while working in the mines some years before the start of the series.
While Rosalind Walker (Roz) was staying with Theo for a "girl's night", Jesse rang a bell indicating that he needed something. Theo explained that Uncle Jesse had seen something while working in the mines years before and had been unstable ever since. Roz went with Theo to check on Jesse and was very disturbed by him. Theo and Roz later explained Jesse's situation to Harvey Kinkle, who had seen something in the mines as a child and insisted on speaking with Jesse.
When Harvey tried to speak to Jesse, Jesse attacked him and Harvey, Theo, and Roz had to work together to restrain Jesse to his bed. The three began to see visions of the possessed Jesse taunting them. Sabrina Spellman learned this and realized that Jesse was possessed. She astral projected into Jesse's room to speak with the demon but is nearly killed and Ambrose had to save her. She then convinced Harvey to take her into the mines to try to learn the demon's name. There, she found a broken tablet identifying the demon as the Devouring Worm.
Lilith, disguised as Ms. Wardwell, gave Sabrina an exorcism rite, supposedly developed by Edward Spellman. Sabrina, Hilda Spellman, Zelda Spellman, and Lilith go to the Putnam's house and perform the exorcism, throwing the worm and tablet down a well. The Spellmans received a phone call the next day from Joe, requesting funeral services for Jesse, whose heart had given out in the night. Unknown to the Spellmans, Lilith killed Jesse with a voodoo doll, stating that the Dark Lord required Sabrina to perform an exorcism on a mortal and that the prophecy would be fulfilled.