The Nightmare King has opened a rift to the waking world and is ready to invade. The dream chasers must make their final stand and defeat the Nightmare King once and for all.
The gang activate Lunia's hourglass and make their way to Castle Nocturnia, hoping to find the key to defeating the Nightmare King. Waiting for them is a mythical creature determined to protect the castle's secrets.
With Lunia's hourglass broken, the gang start their search for the Sandman which leads to a crash landing in the Murky Realm. When the kids' memories begin to fade, they are offered sanctuary by the Never Witch but can she be trusted?
Nova and the Insomniacs' nightmares are getting worse. Izzie and the gang locate them in the dream world and bring them to the Candy Realm to experience at least one night of sweet dreams.
As a night terror rampages through the Fall Festival, the Night Hunter threatens Mateo's family, forcing him to travel to the dream world and confront the Nightmare King alone.