When they're together, block towers climb high as the sky, and the clouds hide great seahorses and wild, swooping dragons. And when they're apart, they call each other with their special sound:

"Coo-ee, Am-ee!"

"Coo-ee, Lou-ee!"

But then Amy's family moves half a world away. Louie and Amy miss each other very much. But when Amy is awake, Louie is asleep. When Louie is awake, Amy is asleep.

And what happens next is a story for true friends and wondrous dreamers.