Seymour Krelborn, a shy orphan working at a struggling flower shop, stumbles upon a mysterious plant after a solar eclipse. Seymour soon discovers it feeds on human blood. Initially feeding it small amounts, he finds the plant thrives and the shop's fortunes improve. As the plant grows, it becomes a local sensation, drawing customers and media attention. When Seymour's coworker's abusive dentist boyfriend threatens his coworker, Seymour is tempted to feed him to the plant. Instead, the plant reveals its alien origins and plans for world domination.