Reopen Manhole Covers...
	Various Achievements...

As you near the end of the game, you will obtain Doc's eye. Go back to the safe house and proceed through the kitchen, at which point you'll find all fast track routes closed. You can open them again, though, by heading back to each cleared area from the safe house. Find the manhole covers and open them once again. That will help you out a lot in the very near future.

Complete the following achievements to unlock Microsoft Gamerscore points.

Achievement	How to unlock
BOB is your best Friend (10 points)	Pick up a backpack (Bug-Out-Bag).
Baby Steps (30 points)	Finish Game in Chicken Mode.
Betrayed! (90 points)	Survive the Ambush at the Church.
Buckingham Palace (30 points)	Get into Buckingham Palace.
Burninated! (30 points)	Kill your first zombie with a Molotov Cocktail.
CCTV Is Watching You (90 points)	Hack all of the CCTV junction boxes in London.
Crossbow Kill (30 points)	First Kill with the Crossbow.
Epidemic (30 points)	Kill 100 Zombies.
Expanded Backpack (30 points)	Get the XL BOB.
Expanded Storage (90 points)	Get the XXL BOB.
Headshot! (10 points)	First Headshot with a gun.
I Survived! (90 points)	Finish Game in Standard Mode.
Let's Go Shopping (30 points)	Get into the Supermarket.
Outbreak (10 points)	Kill 50 zombies.
Pandemic (90 points)	Kill 200 zombies.
Safehouse (10 points)	Make it to the Safehouse.
The Nursery (90 points)	Get into the Nursery.
Tower of London (30 points)	Get into the Tower of London.
Unbreakable (90 points)	Reach a Survivor Score of 2000 points.
Unstoppable (90 points)	Finish Game in Survival Mode.