This act starts with Marcus needing to find Alpha squad. Take some cover behind a wall. The helicopter will take out the "Reinforcements".
On your way to the church, Marcus can grab an enemy weapon for a backup. Climb the stairs to the church.
Enter the church. Follow the hallway to the left. You will come to an open area where the squad will be attacked by Locust.
When the Locust squad is dead head to back of area and exit through opening to the right.
Follow the path to the stairs. Climb the stairs to reach an open area. A cut scene will begin. Once the cut scene is over some Locust Grubs will attack.
The squad leader wants Marcus to flank the Locust to the left. Go to the left side of this area. Duck behind the columns for some cover.
Get to the second column down and take cover next to it. Aim around the corner to shoot the Grubs.
When the Grubs die, an emergence hole opens. An emergence hole is a where Locust spawn. Kill these new Locusts. The squad will go down the path to the left from the emergence hole. The squad runs into more Grubs. Make your way down this hallway.
Continue along the hallway around the corner to the left. You will see a bridge up ahead and to the right. Cross the bridge.
Walk to the door. One of your squad mates will open it for you. Once in the room take cover any place thatís near you. Move towards the forward and to the left of where you entered.
Another emergence hole will open. Kill the Locust that exit. When they die the gate will open.
Exit through the now open gate. Go down the stairs that are ahead and to the left. At the bottom of stairs go straight to the van you saw earlier. At the van a cut scene will begin.