George Santayana said that those who cannot remember the past are condemned to repeat it. In the case of the ThunderCats, the problem lies in the fact that the past has been lost for the most part. The only record of their history lies within the Book of Omens. When Lion-O opens the book, he finds the pages to be blank. Before he can defeat Mumm-Ra and save his people, he needs to know why the monster wants to destroy them in the first place.

Still at the Tower of Omens, Lion-O is trying to figure out the secret of the Book of Omens. He reasons that maybe the book is a piece of technology that must be activated. While trying to figure out the book, he accidentally activates it and the energy released knocks him out cold. Energy from the book latches on to his soul and pulls it within the book as Snarf helplessly watches. Inside the book, Lion-O meets Jaga and is told that the answers he seeks lie in the past. He must relive a pivotal moment in ThunderCat history in the body of his ancestor, Leo.

Leo is the Thunderian that stood at Mumm-Ra’s side in the previous episode. He is the commander of the cat forces that serve Mumm-Ra. He is ordered to deploy the other animals to search for the war stone on Third Earth. At the animal cages, Lion-O meets Leo’s partner, a tall, female cat. She brings him up to speed as the guards place security collars on all the animals. A riot breaks out and a lizard that looks like a relative of Slithe slams Lion-O against a wall. The riot is quickly ended, and Leo’s partner takes the two leaders to a holding cell. Inside, Lion-O learns of the rebellion against Mumm-Ra. The big lizard and a jackalman discuss an alliance of all the animals against Mumm-Ra. When the war stone is procured by Captain Tygus, Mumm-Ra sends Leo to bring it to him but he makes a bit of a detour. Deep in the bowels of the pyramid, Leo finds three cats forging the Sword of Omens. He then meets Tygus in the landing bay and takes the Eye of Thundera from him. Joining the two together, Lion-O now holds the blade he knows in his own time.

Leo returns to Mumm-Ra to challenge him. Since Lion-O is in control, he has no way of knowing that Mumm-Ra’s gauntlet has three other stones in it, giving Mumm-Ra unimaginable power. As the two clash, the power of the Eye manages to dislodge one of the stones and Leo thinks that removing the other two will be easy until Mumm-Ra uses the other two to create armor. Still Leo manages to knock Mumm-Ra off the platform they are fighting on. He uses the break to release all of the animals and calls them all to revolt against Mumm-Ra. When Mumm-Ra returns he begins to gain the upper hand until Leo realizes that he too can attach the stones to his claw shield and creates an armor of his own. Now on equal grounds, Leo knocks Mumm-Ra out of the pyramid into space. The battle continues in space until Mumm-Ra is thrown back inside and Leo strikes his gauntlet with his sword, dislodging the two remaining stones. Leo places the stones in his claw shield and the battle is won. With Mumm-Ra defeated, he retreats into his crypt as his pyramid is caught in a magnetic storm. The pyramid comes crashing down on Third Earth and Lion-O is returned to his body before the impact. He awakens with the ThunderCats standing over him and he tells them that he knows what they have to do.

The Book of Omens has given Lion-O knowledge of Mumm-Ra’s quest for power and the origins of his people. Now he must unite the animal races and find the other three stones that Leo once embedded in the claw shield in order to defeat Mumm-Ra once and for all. This episode has given fans a lot to look forward to. Until now, the only member of the original Mutants of Plun-Darr we have seen is Slithe. This episode featured monkians, jackalmen and vulturemen, so hopefully we will see their future counterparts as well. We also see Mon-star, main enemy of the SilverHawks. Hopefully, they will be in an upcoming episode along with the TigerSharks, who were also among Mumm-Ra’s slaves. This episode really bridged the gap between the original show and this new incarnation. It shows that the writers are going for something different but not abandoning the core concepts that made the old show great. I really look forward to seeing how this season progresses and any other surprises that are in store for viewers.