while trying to help the unlucky person out.

You'll start by crossing some rooftops. Keep going until you reach an office building. Head inside through either window and make your way to the main office area, which is pretty much straight ahead down the hall. Go past the front desk, and you'll be in the main office space. Keep an eye out for Molotov cocktails on the dresser to your right; you might also find some upgraded weapons or extra ammo on the desks.

Next, you'll need to cross some wooden planks outside a window to get to another office building. Once inside, open up the first-aid station you see for some healing items. Also, check the steel racks in the room for ammo caches. As you start heading down the staircase, be really aware of your surroundings. Boomers or Hunters can sometimes come up from the other direction, so be ready to fight or evade.

Things can get pretty hairy on the third floor. I've found that both a Tank and a Witch often spawn here. It's a tight space with all the cubicles, so if you run into a Tank, you might have to lure it back up the stairwell to give yourself more room to maneuver.

The cubicles themselves offer decent cover for the Infected, so you'll have to carefully peek into each one to make sure the floor is clear. As always, it's a good idea to explore all the rooms before you make a break for the green exit sign.

Continue on to the second floor. Honestly, it's pretty much the same layout as the floor you just came from. Just like the third floor, you'll want to sneak through the cubicles and rooms carefully before heading to the opposite end.

The first floor is your last stop inside before you head back outside. Make sure to check all the rooms here and take down any Infected hiding in the side rooms. Once you're sure it's clear, exit the building through the front door onto the street. Now, if you didn't have to fight a Tank inside this office building, there's a pretty good chance you'll run into one out here on the street.