For the player in the security systems, continuously move to the next system to cover your partner. Each new area will be unlocked when the other player activates it through an in-game computer.
Follow the alley to the first computer, then activate the defense system for assistance from the other player. Follow the stairs upwards, then when the next staircase is reached, the player will be attacked from both sides by enemies. After defeating them, follow the staircase upwards and kill the two enemies at the top. Activate the next defense system and go through the window to the next area where there will be ground units and helicopters. When the area is clear enough, proceed through the warehouse to the right and activate the defense system on the other side. Continue past the gate that was opened by the defense system and get to the other side of the construction area to end the level.
