It doesn’t take much time playing Prey to realize you’re making a lot of choices that have inevitable consequences. These choices lead to several endings. One of those is available to you fairly early in the game, before you even figure out much of what’s going on.
Getting there is closely tied to the "Who Is December?" optional objective. In fact, this ending is actually a task in that objective. You will still have to play through a few main story objectives, but doing this will get you to an ending much earlier than playing the game to its actual conclusion. But we should emphasize that this is just an ending (and not a very good or satisfying one).
There are several steps necessary to get to the point where you can end the game.
Get Alex’s safe keycode from December’s corpse after January destroys it.
Search Alex’s Office Safe and get Alex Yu’s suite keycard. There are two ways to get to the safe in Alex’s office. Look for the crate against the wall to the left of the desk — you’ll need Leverage 2 to lift it, but there’s a maintenance access panel behind it. The other way in is to wait until "The Keys to the Kingdom," late in Prey, when you can smash through the Looking Glass display hidden in the wall behind the desk. Use the keycode from December’s corpse to open it.
Search Alex’s Room for the Escape Pod key. You can get the EP-01 keycard from Alex’s Cabin in Crew Quarters — you’ll explore Crew Quarters during "Gathering Echoes." It’s really easy to miss — the keycard is under the globe next to Alex’s bed.
Now you need to get back to Alex’s office in the Arboretum. Getting to the escape pod takes some work, though. If your hacking is high enough, you can use Alex’s computer to extend the bridge to the escape pod, but it’s also possible to build your own bridge using your GLOO cannon.
Climb up onto the roof of Alex’s office, then look for the wooden shelter-things. (Google tells us these are called pergolas, but we’re pretty sure that’s a made-up word.) Get to the roof of the "pergolas" and turn toward the escape pod. Use your GLOO cannon to give yourself footholds along the metal girders.
Escape Talos 1
When you get to the escape pod, use the EP01 keycard you found in Alex’s room to get inside. Turn around, then push the button to close the door. Then you can use the computer screen to launch the escape pod and just kind of … quit.