While Wilykit and Wilykat are out in the woods making a map of the area as per Tygra's instructions, they hear a commotion and go to investigate. The cries for help are coming from an oldWolo Traveller who is being robbed by what appear to be two gargoyles. The Thunderkittens intervene and rescue the Wolo but the gargoyles make off with his bag containing a gold bracelet, a gift for his daughter's wedding to which he was heading. The Wolo informs them that the gargoyles work for Baron Karnor who lives in the nearby Black Tower
Wilykit and Wilykat head for the tower and upon reaching it, find that there is no way into it. Wilykat tries to force open the rusty old lock on the tower's door while Wilykit circles the tower to look for another entrance. When she returns she finds that her brother has disappeared without a trace. She calls out to him but gets no response.
Meanwhile, Lion-O is enjoying a relaxing swim in a small lake near Cats Lair. As he gets out, the Sword of Omens warns him that a ThunderCat is in danger. Using the sword's "Sight beyond sight" vision, Lion-O sees Wilykit desperately searching for her brother. He immediately rushes off to the tower that he saw in the sword.
When Lion-O arrives, Wilykit tells him what has transpired. Lion-O tries to force open the lock just as Wilykat had done. Immediately a trap door opens beneath them and both Lion-O and Kit drop down and find themselves inside the tower. They call out to Wilykat who replies that he is in a cage at the top of the tower.
As Lion-O and Wilykit start to make their way up the tower, they come across a trick staircase which prevents them from climbing it. Lion-O elongates the Sword of Omens and uses it as a pole vault to get him and Wilykit up the stairs. As they continue their ascent, an iron fence suddenly drops down from the top separating Lion-O and Wilykit. They both continue on their separate paths.
Lion-O encounters a giant hungry Octopoid with snapping claws but manages to subdue the beast. He also manages to barely jump across an extending acid-filled pit and bypass blades that shot down from the ceiling. Wilykit on the other hand first contends with having to cross a slim bridge over a raging inferno and then a room filled with laser-shooting statues and finally a hallway packed with swinging blades.
At this point Lion-O and Wilykit have reunited and finally locate Wilykat in a cage, hanging from the roof. They free him and at that point a door opens and they hear a voice telling them to enter. They cautiously enter the room which turns out to be the baron's treasure room. There they find the baron's dead body sitting on the chair. The voice that told them to enter turns out to be a recording and the doors of the treasure room shut by themselves, trapping the three ThunderCats.
While Lion-O, Wilykit and Wilykat are searching for a way out, a panel opens in the roof and a piece of jewelry is dropped into the room. Wilykit recognizes it as the Wolo's wedding bracelet. The ThunderCats make their way out via the roof and emerge at the top of the tower where they find nothing but stone gargoyle statues. The statues suddenly leap to life and attack the Cats. Lion-O summons the other ThunderCats and they arrive shortly in the ThunderTank and help to fight off the gargoyles. The Cats then head back home but not before stopping at the Wolo village to return the bracelet.