It starts in the “waiting room”, which is the crewmates’ ship, everyone is safe and there are no imposters.
They then arrive at the skield, which is the imposters’s ship, and are given tasks to take it over. They soon discover that one crewmate has been infected by the parasitic imposters. The imposter then kills a bunch of crewmates until the crewmates finally throw the infected CREWMATE out of the ship. The imposters still live on the skield, so the crewmates leave.
The crewmates then head back to their home planet, on which is Mira HQ, but the find that the skield has already been there and dropped off more imposters, when the crewmates finally figure out who they infected, they are able to study them in their lab. They find out where the imposters live by looking through their telescope.
They get back in their ship and crash land on polus, the imposters’ planet. They are there to wipe out the imposters.