Arthur is a dog with a secret. More than anything in the world he loves to play his violin, but he's too scared to do it in public because, well, what if he's bad? What if people laugh? What if he makes a fool of himself?! WHAT IF?

But the song in his head and the dream in his heart just won't stay quiet. So, when he's invited to take part in a jam session, he creates the ultimate disguise - a post box costume! And when it falls apart, Arthur doesn't.