Once upon a time a violent, mean, selfish Tyrannosaurus roamed the land, and all the other animals feared him. One day, while chasing other animals, the Tyrannosaurus falls into the ocean. The Elasmosaurus, who lives in the sea, saves his life, and the Tyrannosaurus says thank you for the very first time. From that day, the land creature and the sea creature become best friends.
A female Maiasaura finds a lost egg in the forest and decides to look after it with her own egg. Surprisingly, a baby Tyrannosaurus hatches from the egg. The greathearted mother accepts and raises him as her own son, Heart. One day, Heart goes to pick berries and comes across another Tyrannosaurus. The foster son of the Maiasaura discovers his real identity.
Although Tyrannosaurus storms around saying that power is everything in the world, he realizes he is getting weaker with age. After his tail gets bitten in a run-in with Masiakasaurus, some young Triceratops nurse him back to health. Touched by their innocent hearts, Tyrannosaurus begins to feel love for these new friends even though he might have eaten them under different circumstances.
A little Pterosaur lives on top of a rocky mountain, where his mother teaches him to be kind and to always help others in need. One day, a huge Tyrannosaurus falls down the mountain and is injured as he tries to catch the little Pterosaur. Remembering his mother's lesson, the little Pterosaur decides to take care of the injured.