Alexis and Alice sit on their balcony and look at the sky. They know that Earth is a hospitable planet - the only one in our solar system where there is life! But, like all humans, our two little friends want to learn everything about the sky. They dream that one day they will board a spaceship and travel to Mercury, Venus, Pluto, Mars... And then, they will visit other solar systems, distant and unknown. After all, humans have always studied the sky, trying to learn the truth: Is there, perhaps, life on other planets?