A cosmic case of UFO's intergalactic intrigue and out of this world romance launches Scooby, Shaggy and the Mystery, Inc. kids into their most unearthly adventure ever! Stranded in a remote desert town, the gang soon discovers the place is crawling with flying-saucer buffs, secretive scientists.. and less -than- friendly extraterrestrials! Then, after being chased by aliens and beamed aboard a UFO, something even weirder happens to Shaggy and Scooby - they fall head over heals in love! As clues to the mystery of the alien invaders lead them from a top-secret government research base to a huge network of caves hidden under the town, our love-struck heroes join the rest of the gang in a race to crack a case the redefines the term 'far out!'.