After a period of harsh rain, the Great Valley is partially flooded, and covered in debris. Littlefoot tries to play with his friends, but they are preoccupied: Cera and her father are removing a large log from their nesting area, Ducky and Spike are relocating their nest with their family, and Petrie has gotten a cold. A bored Littlefoot wishes for a brother, but eventually explores on his own, and discovers a large area flooded by the rains. The adults advise their children to stay away, fearing dangerous creatures from the outside may have been washed into the Valley. However, Littlefoot returns, and meets Mo, a playful young ''Ophthalmosaurus'' that had been caught in the floodwater.