Reopen Manhole Covers...
	Various Steam 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 indicated task to unlock the achievement.

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