Once upon a time there lived a very sad man up in the silvery moon. Since countless years he's been staring down to planet earth and thinking of his greatest wish: being among humans, just once in his life. One night his wish comes true. He manages to jump on a passing comet that brings him to the place of his dreams: earth. But earth isn't as peaceful as he imagined it. A fierce general considers him an intruder and strives to capture him. Only the 8-year-old inventor Lucia finds out about the true nature of the harmless alien. She rescues him from the General's dungeon and guides him to the castle of her famous grandfather, the inventor Professor Bunsen Van der Dunkel. An entertaining shortfilm for all ages, based on the classic picture-book by Tomi Ungerer.