Terrans are contacted by an alien civilization, nothing like anyone had ever imagined, not a war-like race, not wise overlords, just alien, and so alien that communication is not only difficult, it is just impossible. In fact even the concept of communication seems to be impossible for the alien race to comprehend…
After the excitement and the media frenzy, the aliens just fade from attention, and only a small group of people stay interested. At one point the aliens leave and humans mount an expedition to follow them. They get into the aliens’ ship, and tag along in the voyage, and finally, after a long time, end up on a planet of those aliens, and the humans settle there. They slowly learn and teach a way to communicate with the aliens, learning many things about themselves in the process…
Generations pass before actual communication is possible, and before the Stowaways change enough to be able to comprehend the aliens and how they think. The descendants from the Stowaways mount an expedition back to Earth, and they arrive, after years of traveling back, to a Earth that is now almost as alien to them than the original Aliens were to them centuries ago…