Animorphs

The story of Ellimist, a being who can alter space and time in unexpected ways.

Marco is determined to save his father from the Yeerks.

Cassie believes her strange dreams are just a side effect of having been given the alien power to morph into an animal, but when she learns that Tobias has been having the same dreams about the ocean, they realize someone is issuing a call for help.

The Animorphs are in real trouble when they transform into flies to invade the new base of the alien Yeerks, and Jake becomes the enemy after falling into the Yeerk regeneration pool.

Marco is a reluctant Animorph, having been given the ability, along with four other friends, to change into animal forms by an Andalite prince, an alien who wants help in stopping an invasion of the enemy Yeerks, but when he discovers that his mom, who he believed was dead, has been taken over by the Yeerks, he finds a reason to fight.

The final battle between the Yeerks and the Animorphs approaches, but the resolution is uncertain.