While Sheriff Lucilia Cable searches for Alec unsuccessfully, Abby theorizes that it was more than an accident and retrieves his video journals from Daniel Cassidy. When one of her patients, Susie Coyle, escapes from the hospital, Abby and Matt follow her into the swamp. There, Abby encounters Swamp Thing - a creature that Susie later identifies as Alec Holland. While Alec struggles to understand his metamorphosis into the monstrous, plant-based creature, known as Swamp Thing, Avery meets with Jason Woodrue, the scientist who initially developed the biological accelerant responsible for the "green flu" and orders him to halt the epidemic. And Maria Sunderland reaches out to Madame Xanadu in order to communicate with her dead daughter, Shawna.
When CDC researcher Abby Arcane returns to her childhood home of Houma, Louisiana, in order to investigate a deadly swamp-borne virus, she develops a surprising bond with scientist Alec Holland - only to have him tragically taken from her. But as powerful forces descend on Houma, intent on exploiting the swamp's mysterious properties for their own purposes, Abby will discover that the swamp holds mystical secrets, both horrifying and wondrous - and the potential love of her life may not be dead after all.