In one of the missions in Prey, you go to meet December. However,
just as you get there, January kills December.
However, it's possible to kill January before then - there's even an achievement for it. What happens in that case?
21 Answer
December "takes place" of January, but instead of pushing you towards the destruction of Talos I he/she will push you towards the escape in Alex's escape pod (false ending). Other than that - no differences in gameplay.
2