Stage 3: The Sewers

Walkthrough: Funnily enough, most this level doesn't actually take place in sewers! After leaving the safehouse, you make it out into the loading area of a warehouse. After using the lift (which summons a Horde!), you will make your way into the warehouse, which has entrances to the sewer in the basement. After traversing through the sewers, you will find yourself on the streets in front of Mercy Hospital, where your next safehouse is in the entryway.









Horde Choke Points

• In the warehouse stairwell. They can come from both directions, but the space is narrow enough that it's easy to pick them off.
  
• In the small tunnels in the sewers. Be careful, though, as at the corners, Infected will often drop from above to attack you, and that's not good for your health at all.

Tips and Tricks

• You can shoot the pumps at the gas station to make it explode! Great for eliminating tanks that have been lured into it, or if you just want to see some awesome fireworks.
• The Infected take a bit to show up after triggering the lift, which gives you enough time to sprint to the warehouse, where it is significantly less open and easier to kill them.
• Through the sewers area there are almost always two paths. If one path is blocked by a Witch, just take another. The tunnels are your friend, but you can find more supplies in the main area.
• Unlike Stage 2, advanced weapons don't spawn on tables. Instead, they seem to spawn just about anywhere. The most common place seems to be in the sewers next to the dividing tunnel between the two different sewer sections.
• The ambulance always has a medical supply inside. It can be either a first aid kit or pills, but the lower the difficulty, the higher the chance it'll be first aid.

Stage 4: The Hospital

Walkthrough: Time to scale that there hospital! Starting at the bottom floor, you have to traverse each floor, going through different stairwells to reach a working elevator. Once you reach the elevator, you have to hold off a Horde until it arrives, and then you can go to the upper area of the hospital. The upper area is under construction, which makes it hard to tell where to go but easy to see Infected. After going through the construction area, you reach the safehouse and the level ends.









Horde Choke Points

• The upper lobby office. It has two double doors that take significant damage before being destroyed, letting you handle zombies with ease.
• Any of the stairwells, for obvious reasons. Stairwells are your friend in this game!

Tips and Tricks

• You'd think a hospital would have medical supplies everywhere, but this one doesn't. Sorry!
• The Witch normally spawns in one of the corridors, the lobby office, or a stairwell. In other words, you almost always have to kill the Witch for this level.
  
• You may think this is totally unfair, but the elevator section of the level is the first time you find out zombies can break down walls. And they will. Constantly. No area is safe in that sequence, so don't get cocky!
• The elevator sequence introduces a special kind of exploding tank: the oxygen tank. Upon shooting it, it blows air for a few seconds before exploding. Great for parties!
  
• Listen to the dialog in the elevator. It's hilarious!
• Most of the upper area has no walls, which lets you shoot Infected from a ways away. However, it also makes it easy for Boomers and Smokers to get you with their special.

Stage 5: Rooftop Finale

Walkthrough: Oh boy. This is the hardest level in the whole campaign, and for good reason. You fight countless Infected, both special and common, and also face down a few Tanks. Thankfully, Witches don't spawn with the waves of enemies. Make your way to the roof (only a corridor away!), trigger the radio, and prepare for the fight of your life.

Horde Choke Points

What choke points?

Tips and Tricks

• There are two full refitting areas in this level: the starting safehouse and the area near the radio. In both areas you get four first aid kits, advanced weapons, another pistol, and an ammo stash. Awesome!
• Much like the vents in Stage 2, the Tank has to crawl through the windows of the radio room, slowing him down significantly and making him much easier to kill.
• There are tons of grenades on the two platforms attached to the radio room by piping. Get those grenades and use 'em to your advantage! In a similar vein, there are also throwables to use, so take advantage of them.
• Standing on the top of the radio area is the single best place to survive the Hordes. They have to leap up to get you, giving you plenty of time to shoot them in the face. You can always survey the surrounding area for nasty Specials.
• Watch out for Smokers. They will drag you from your perfect spot and into a Horde if you aren't careful. On Expert, this is killer.
• When in trouble, jump in the radio room closet and kill the Hordes. It's only got one entrance and with several people inside, becomes virtually impregnable. It's not a choke point, though, because it only holds out until a special comes along, and then you die.
  
• Ignore the minigun. Smokers can drag you off and Hunters can pin you. It's not worth exposing yourself.

Congratulations! You've finished No Mercy. Ready for the other campaigns?