When you have control of your primary team, head down the ramp nearby and into the Collector base, follow the winding pathway around until it empties out into a large open room. Kill the three Collector Drones in the room to the right here and the reinforcements that arrive soon after. Move to the other end of the room and you will receive a communication from your team member in the vents telling you there is an obstruction in the vent. Move into the room opposite the entrance and use the green valve (1/8) here to assist.
Move to the right of the valve and look down the ramp to the left. There are three Collector Drones here and one of these will become Harbinger. You didn’t think it would be that easy, did you? Once they are defeated, move down and vault the cover here. Hit the green valve (2/8) on the left and as you do, more Collectors will fly onto the platform from the right and unsurprisingly enough, one of these guys will become Harbinger. Once they have been capped, continue along the pathway here; hit the green valve (3/8) here and vault up into the raised area at the end. It’s always a good idea to kill any Collectors that arrive before hitting the valves, especially on Insanity difficulty where you will need more time.
Activate green valve (4/8) in this room. Continue to the right and take cover as you turn into another open area. Below and to the right, a group of 6-7 Collector Drones will be waiting for you and one will become Harbinger. When you have dropped them, look across the room and slightly to the left to see the next valve.
Once you know where you are going, drop down into the room below and use the various platforms to vault across to the other side of the area. About a third of the way across another group of two Drones and Harbinger will land. Dispatch them quickly before running over and hitting the green valve (5/8).
Continue into the hallway to the right and disable the next green valve (6/8) here. Follow the passage around the corner and eliminate the three drones here. Take cover behind the raised area to the right at the end of the hall and you should see the next valve in front of you at the near end of a bridge leading to a large platform. Stay in cover here and defeat the Collector Assassin and any other Drones in the immediate area. When they are dead, vault up to the platform and quickly run up to activate the green valve (7/8) and take cover.
On the platform across the bridge 6-7 Drones and Harbinger will fly in to keep you at bay. Continue to move up and eliminate them as you go. When all the enemies are all dealt with and the coast is clear, make your way over to the left to hit the final green valve (8/8) to watch a short story scene.
During the scene and the subsequent conversation, you will need to set up another team and select another leader for a secondary team. You can also send one of the guys to escort your newly rescued crew members back to the Normandy.