Wally doesn't understand why he's a different color than his brothers and sisters. On top of that, he can't purr. All he can do is screech. The harder he tries, the worse he sounds. He wants to believe his mother when she tells him he'll purr when he's happy, but he doesn't understand what it's going to take to make him happy.
So Wally begins a journey to discover the reason for his differences and hopes he can find something to make him purr. Instead, what he finds is the true meaning of love and acceptance.