Olive’s friend has moved away, and Olive wishes she could visit her. A little green envelope, lost in the bottom of the desk drawer, knows how Olive feels. It, too, wants so much to travel, and imagines zipping up and down conveyer belts and bouncing along in a mail bag, on its way to deliver an important letter. An old postcard reassures that for every occasion, there is an envelope … but it seems like it will never be the little green envelope’s turn.

When Olive’s grandpa suggests writing her friend a letter, the little green envelope hopes and hopes that it will be chosen to carry the letter to its destination — but will it be a perfect fit?