A rat is about to spend a quiet Sunday among trash cans, sewers and wastelands, when a seductive little extra-terrestrial lands wiggling in front of him. Here he is all exhilarated. And off we go for a day full of adventures. But in the public garden, the guard's dog will spot the two lovers. Our rat is taken prisoner to the great despair of her alien who returns to her home. Fortunately, her friend, free again, manages to join her.