Batman, Constantine, Zatanna and Swamp Thing have to work together to stop Solomon Grundy, who is trying to use a magical gem to raise an army of zombies and also turn anyone living into zombies.
This episode contains examples of:
- And Then John Was a Zombie: Batman and Zatanna are transformed into zombies when the crimson moon comes into effect (it doesn't last, though, as the gem is destroyed, returning everything to normal).
- Jerk with a Heart of Gold: Swamp Thing doesn't particularly care for humanity, but fights to save it anyway. He cares more for humanity at the end when people show appreciation for his efforts.
- No-Holds-Barred Beatdown: Attempted by Grundy on Swamp Thing during his Villainous Breakdown; however, Swamp Thing No Sells all of Grundy's punches.
- Villainous Breakdown: When Grundy's plans are foiled, he attacks Swamp Thing in a rage.
- We Can Rule Together: Grundy attempts to convince Swamp Thing to join him to destroy humanity, in return for sharing power with him. Swamp Thing doesn't accept.
- Zombie Apocalypse: Grundy intends to turn every person on Earth into a zombie (whether living or dead).
