From the introduction:
Christmas on the Moons takes place at the A-1 Colony on the Moon, five hours after the characters fled the research center leaving the alien and the huge explosion behind (CotM). As they arrive at the colony they believe themselves to be safe, but they quickly learn that the reality is completely different. The colony has been under attack for days by the same species of aliens, and the remaining survivors are now hiding in dark places hoping to be rescued before the monsters get to them. As the story progresses the players will encounter dead crewmembers, aliens and survivors as they visit the different locations at the colony in search of weapons, food, answers and last but not least a pilot who will be able to take them home.
There are some “most likely” outcomes of this scenario, but none of these are in any way decided by me. This story ends when either you or the players decide to end it. If this happens when the characters manage to escape the colony in a shuttle towards Earth, or it happens as the last of them are hunted down by the aliens only to be killed or captured, is not decided by me. I will later lend you some advice on how to run the story and, how to possibly end it, but it will ultimately be up to you and your players to decide how your game ends.