In the shadowy depths of the swamp, the creature once known as Dr. Alec Holland, transformed by a tragic experiment into the Swamp Thing, continues to protect his watery domain. Elsewhere, Dr. Arcane, believed to be dead after the explosion that first birthed the Swamp Thing, is very much alive. Arcane, obsessed with immortality, conducts genetic experiments at his secluded mansion in an attempt to unlock the secrets of eternal life. His work has led to the creation of mutated creatures that roam his estate, byproducts of his relentless quest for rejuvenation.

Unaware of her connection to this dark world, Abby Arcane, Arcane's stepdaughter, arrives at the mansion seeking answers about her mother's mysterious death. Her investigation leads her to the swamp, where she encounters the Swamp Thing and a strange bond forms between them. As Abby delves deeper into her stepfather's affairs, she uncovers the horrific nature of his experiments and the extent of his madness. The destinies of Abby, Arcane, and the Swamp Thing become entwined, setting the stage for a confrontation that threatens to unravel the secrets of the swamp and its monstrous guardian.