Mia is an imaginative young girl who happens to be afraid of almost everything. One day Mia invents a brave new imaginary friend she calls Frida. With her new best friend by her side, Mia has the courage to face any and all of her greatest fears.

As the years pass and Mia grows up, people tell her that she is too old to believe in all these fantasies. Eventually Mia starts to forget about Frida, until Frida is no longer there. Mia doesn’t know how to face her fears alone so she decides to avoid everything and become invisible to the world.

One day, Mia looks inside her closet and notices that a funny little creature is hiding inside. It turns out that this creature is someone else’s imaginary friend that was abandoned because he was broken.

The poor creature couldn’t disappear, and who would want an imaginary friend that can’t become invisible?

They decide that together they will search for their best friends and have many great adventures along the way, but without noticing, they become best friends themselves.