A new group of strange knights has arrived in the kingdom.

When Merlin is asked why Bog Lake is boiling, he learns that the key Lance can use to free Sir Lancelot is within. Tone creates a portable shed with scuba equipment of vines so Artur and Lance can search for it. The three, Wally, Brick, Breeze, and Lug avoid the Warlords on their way out thanks to a Merlin's decoy, but Morgana learns of the key about the same time the Warlords realize the trick. The Warlords attack just after an underwater chasm opens and the key falls in, and cut Lance's scuba so he topples in as well.

The knights have left Camelot with only the squires Tyronne and Everett left to defend the castle.

Merlin's evil side is let loose.

Despite Darren, Wally, and Brick fighting alongside him, Arthur is effected by Blinder in battle long enough for Hammer to wound him and Blackwing to steal Excalibur. Wally blames himself for not being able to protect him from every harm, so moodily avoids the others - then accuses the others of blaming him for their own failure. Then he defects to join Morgana, giving her Merlin's wand.

During a battle too early to tell which side is winning, the Warlords abruptly retreat when a lunar eclipse begins. Merlin remembers too late that it has transported the three attained Keys of Truth through an unspecified time in the twentieth century, which Morgana has told the Warlords. The portal is Grinlap's tree, so Arthur, Darren, and Tone return to time-travel again and reclaim the keys, but the Warlords are ahead of them. Annoyed by their confrontation in his home, Grinlap watches the Warlords go through the portal then throws the knights in.

It's not the flying that worries Sir Breeze, its the landing.

Merlin dreams that he is attacked by the monster of Fear Island, the one place where his magic cannot function and where Tone's key is. He sends the Knights of Justice there with the warning that the creature's hideous appearance will disintegrate any who view it and they must use all their resources and wits to be the first to survive the isle.

Arthur and the Knights trick the Warlords away from Castle Morgana so they can retrieve Merlin's magic book.

Morgana tricks her way into Camelot using a duplicate Arthur.

The Purple Hoard has fallen ill and Morgana plans to use the disease as a weapon.

The knights have to figure out how to break a winter siege at a neighboring castle.