Every time a bell rings, an angel gets her wings.
Each Angelwing book tells the story of how a little angel earns her wings by being a helper to a child with a problem. The children's problems are simple and surmountable - ranging from a failure of courage to being clingy to being unkind to animals. Each angel is especially suited to the task at hand, and is guided by a particular Archangel.
The Little Angel of Imagination helps Louis watch less TV and make up his own games to play.