You must make your way through the walled-off streets and find a way into the chots' underground headquarters.

The first area you'll come to will feature a large open area and an alleyway that leads to a large, locked gate. At the end of the alley is a small room with three weapons dispensers. Stock up if you need 'em. Go back to the open area. There are two doors leading to tank bays here - the one you exited from and another one. Enter the other one. Go through the small door on the platform to reach the elevator.

Ride the elevator up, then exit. Go up the stairs to the elevated walkway. There's a chot here, and you'll want to possess it if you can. If not, just kill it and move on. At the end of the walkway, you'll come to a dead end. Jump down. If you're a chot, you'll be safe. If not, several chots will begin attacking. The cop will be hurt in the fall, so quickly jump out and possess a chot. Make sure you have a pak before you proceed.

You'll see a short wall with some pipes on the far side. Jump onto the wall. The large pit below you is the entrance to the sewer. Jump down, using the pak to prevent injury. Follow the tunnel around, past the locked door, to a walkway above the sewage. Let the chots and the cops fight before proceeding and help in the battle if you choose. On the walkway you'll also encounter a chot and a light cop. Deal with them as you see fit.

You'll come to a gap in the walkway near three pistons. You must jump to each of the pistons to reach the far side of the room. Use the pak or just dump your host in the waste and glide as Bob. Get to the third piston and wait until it's at its highest point, then jump and glide to the walkway. Be careful on the next segment - it's unstable.

Jump and glide across the walkway to avoid falling in. At the end, you'll see a locked door and an area blocked by some lasers. Luckily, a fallen cop is blocking the lowest laser, letting Bob crawl through the gap at the bottom. Possess one of the chots in this room, preferably the one who isn't busy eating. Then, activate the console to restore power to the outskirts.

Disable the barrier with the console, then go through the now-unlocked door across the way.

The door leads you back into the chot tunnel. Head right and straight across the walkway. Do not ascend the stairs. Instead, go through the door beneath the stairs. Follow the tunnel to the end, where you'll find the chot behemoth doing a number on a light cop. Possess the behemoth, then head back through the tunnels. Now, go up the stairs.

A door at the top of the stairs will lead you back to the streets. The chots and the police are still fighting, but you can easily take them all in your new host. Get the cops first - their machine guns will do a number on you. Now, run down the street away from the locked door.

Open the door in the next area and fight the chots if they attack you. Continue down the street and dispose of the bazooka-toting medium cop. The door will only partially open, so you must depossess the behemoth and go through as Bob.

Some cops on the other side will open fire on you, so quickly go for cover and possess one as soon as you can. Enter the tank bay and up the steps. You'll be near the laser wall you deactivated before you headed into the sewers. If you haven't disabled it yet, get a bazooka and shoot the controls behind the barrier.

Now, enter the elevator and head up to the lab.

You don't need to do too much in the laboratory area, but it will mark the end of this section.

Leave your previous host in the elevator, then possess one of the scientists in the hallway. Follow the hall around to the control center and activate the behemoth creation system by using either of the consoles. Run down the hall to the large door near the elevator.

A large metal door will prevent further access to the room beyond, but once you try to open it a behemoth will come bursting through. Possess the behemoth, rampage a little if you're so inclined, then go to the large door just to the left if you're facing the elevator.

The behemoth's weight will activate the pressure plate, and the door to the lift will open. Get on the lift and watch the in-game movie.