Leon quickly recovered from his gunshot wound in the sewers of Resident Evil 2 because that’s a great place for quick healing. Now it’s time to go rescue your new friend.
Unfortunately, you can’t follow Ada directly. When you regain control of Leon, turn around and take the left at the intersection ahead of you. Take the lift up to the second floor.
At the top, cross the catwalk to visit the Typewriter and Item Box on the far side of the room. Run down the stairs and drop into the water below.
As soon as you land, grab the Handgun Ammo from the trash pile ahead of you, then head deeper into the sewers. Take the right at the intersection and keep following the sewer until you come to a fork. Follow the left fork first until you come to a fence to grab some Shotgun Shells. Turn around and head back to the fork to follow the right one this time.
Climb out onto the landing on your right, then head up the stairs. The second corpse you pass will have a USS Digital Video Cassette to grab. At the top of the stairs, handle the zombie there and continue into the large room.
Run past the locked Treatment Facility door and around to the left. There are several zombies in here to deal with, so keep an eye on them. You’ll see an electrical panel with a piece you can grab, but ignore it for now. Cross the bridge next to the electrical panel, then follow the walkway to the right and go down the stairs.
Grab the Combat Knife at the bottom of the stairs, then drop into the Lower Waterway.
Head to the west end of the Lower Waterway, then slide down the slope there. Weave past the gross-bergs until you come to a landing on your left. Grab the Blue Herb there.
Drop back into the waterway and continue to the west. When you come to a fork, check the ground around you for some High-Grade Gunpowder, then take the right fork.
Your first G-Adult
Just a little way down the right fork, you’ll run into your first G-Adult zombie. You know the basics of this fight — don’t get grabbed and aim for the giant, yellow eye — but it can be a real drain on your ammo if you’re not careful.
Cable Car Platform
After you face your the G-Adult, continue along the sewer until you can climb out on your left. There’s another G-Adult that will climb out of a pipe on the right, but if you’re quick, you can get past without fighting it.
Head up the stairs and keep climbing until you get to the Cable Car Platform. Head up the stairs in there and then climb the ladder up to the Control Room.
Inside the Control Room, grab the Shotgun Shells and Copy of Emails to Umbrella HQ. When you have everything, drop through the hole in the floor to the room below.
When you land in the next room, there’s a short cutscene. After that, you can poke around a little. Grab the Sewers Map, Handgun Ammo and Sewer Company Pamphlet. Visit the VCR to watch the USS Digital Video Cassette, then head to the Typewriter and Item Box.
Head down to the southwest corner of the room to find your next big puzzle. Pick up the Unlocking the U-Area Door document on the table and read the note pinned to the board next to it. Your goal is to find six chess-themed plugs and place them in the correct panels. You can check out the panels and pieces in this area, but don’t bother picking anything up yet — you can’t solve the puzzle without a bit more work first.
Treatment Pool Room
Exit the Monitor Room through the door on the east wall. Head into the Treatment Pool Room. Throw the switch in front of you, then cross the bridge it lowers. On the far side, turn left and follow the walkway around.
Grab the Red Herb, then pick up the Tool (which will become a T-Bar Handle) off of the table. Head down the stairs a little farther to the next landing to pick up the Delivery Receipt.
Turn around and run all the way back to the bridge. Continue past and follow the walkway around to the right. Deal with the zombie slumped at the end of the walkway, then pick up the Blue Herb. Turn your attention to the safe. Per the Delivery Receipt, the combination is written on the side. Enter the combination you find — 2 left, 12 right, 8 left — to grab the Shotgun Stock (W-870). Combine it with your shotgun to speed up your reload speed.
Turn around and head through the door ahead of you and go down the stairs.
Back to the Lower Waterway
At the bottom of the stairs, deal with the three zombies and pick up the Green Herb. Throw the switch on the right to open the gate, then drop into the water. Turn to the left and go pick up the Hand Grenade.
Go through the gate you just opened back into the Lower Waterway.
Once you’re through the gate, sprint straight forward toward that first landing you saw down here — you picked up a Blue Herb here on your first time through. You’ll have to face or avoid another G-Adult.
Climb out onto the landing on your right and use the T-Bar Handle to open the gate. Duck through, pick up the Shotgun Shells, and take the lift up to the Workroom.
Provoke and put down the zombie on the floor as soon as you walk into the Workroom. Grab the ‘Hiding Places’ Roll Film, Hip Pouch, and Handgun Ammo. Unlock the door and exit the Workroom. There are a few zombies out here (if you haven’t dealt with them already).
Back to the Upper Waterway
Retrace your steps to the southeast and down the stairs to get back to the Upper Waterway. When you hit the water, turn left. There will be a few new zombies in the water with you. Run all the way to the west end, then climb out onto the landing on your left and use the T-Bar Handle again. Run through the gate and down the stairs.
At the bottom, grab the Treatment Facility Key off the wall on your left. Loop around to the right and use the T-Bar Handle again to open the gate on the other side. This path leads up to that weird Y-shaped room near the Lower Waterway, but don’t go that way yet.
Cross back to the side where you grabbed the Treatment Facility Key and climb down the ladder to the Bottom Waterway.
Turn left when you hit the water and cross into the next super gross sewer. Grab the Green Herb next to the corpse, then crawl out onto the landing on your left. Get across the landing and drop down on the other side.
Weave your way through the gross-bergs until you bump into another G-Adult. One or two turns past that, you’ll find another G-Adult. On the other side of that one, cut to the left to find some MAG Ammo, then cut back to the right to find your way to the end of the waterway. Another G-Adult will crawl out of the pipe on your right, but you can sprint past it.
Climb onto the landing at the end, then turn right and go through the door there. Climb up the stairs and go through the next door to find the Supplies Storage Room.