Centrosaurus has been extinct for millions of years.But out of the blue, it appears in Plant Town and mysteriously shrinks into a toy.Where does it come from?And what happens to its body?The Plants decide to solve this mystery!

In the forest,Peashooter,Red Stinger and Sunflower are attacked by a team of dinosaur knights.Surprisingly, their leader is actually a teddy bear by the name of Issac and he rides a Microraptor gui! Under his guidance,Peashooter and his friends enter the Toy City and learn about the secrets of the Sorcerer Samurai and the city from the mouth of Ouranosaurus.

It turns out to be an experiment conducted by Dr Zomboss. However,the experiment goes haywire.Meanwhile, the Sorcerer Samurai has executed his evil plan.Can the Plants stop his plan?