Marshall is one of the main story missions you'll have to deal with when playing Control. This mission focuses on the search for the title character. Below you will find a description of this task.
The task begins at the Research Center. Go straight towards the stairs. There you will encounter the first two opponents that you have to defeat. In this part of the mission you have to keep heading down and repel the attacks of enemies. Watch out, however, for disintegrating barriers. If you hide near one of them for too long, it's going to break.
If you follow this route, you will find yourself in the para-kinesis research section. As soon as you enter this section, you'll encounter a large group of enemies. The whole room is filled with potential shields and cover spots, so you shouldn't have any trouble with dodging enemy attacks.
After the fight, you won't find any more enemies in this section. So you can explore this part of facility as you like. Continue through the door on the opposite side of the room. You will find yourself in a corridor leading to a room with a large three-dimensional model. You'll find a passageway that leads to the control room.
Press the button on the right. It opens a corridor that will lead you to the room below. There you will find an entity that creates a gravitational zone around itself. You won't be able to defeat him. Instead, focus on installing two "batteries" in the doors. These are characteristic hexagons glowing in orange. You'll have to use telekinesis to do that.
After activating the gateway, enter the room behind it. You need to lure the creature that's going to destroy the room. You don't have to do anything special to make the creature start following you. All you have to do is stand still and shoot at the creature from time to time.
When the creature finds itself behind the gate, go to the control room and press the button on the console. This way, you'll open up a passageway to the next corridor. Go further. You will enter a room filled with enemies. During the fight, use pedestals as shields, and the equipment for telekinetic attacks that stands on them.
After the fight, walk through the door on the other side of the room. This way you will find yourself in a room with a large group of Hiss. They won't attack you, so you can easily move on and pass them.
Go through the doors that are in the dark side of the room. Thus, you will reach a room similar to the archive. There, you have to defeat another group of enemies.
After the battle, move towards the checkpoint. This is a characteristic red dot located in the conference room. Take it. This will unlock access to another part of the building. At the end, go to the elevator and interact with it.