Chapter 1-2 is the second level of Resident Evil 5.
The chapter begins with a conversation between Chris and Kirk. There is small storehouse with a crate near the recently destroyed gate. Continue along the path until you reach the exit. Just before this gate is a hole you can jump down and find some gold. Head through the red gate.
Captain DeChant will radio Kirk frequently through this section; foreshadowing an encounter with a B.O.W. Enter the building, search for items and exit via the back door. As you exit, you will notice a half broken ladder, ignore it, and follow the path left. Neutralize the lone female Majini, and continue left down the narrow path. When you reach the end, perform the partner action with Sheva to boost her to the upper regions of the area. Sheva will notify you that she has found the Old Building Key. Deal with any enemies that may be present, and make your way around the building by following the path until you reach the other side of the fence. You will eventually reach a gate where Chris and Sheva must perform a partner action to break it down. Once you enter, you will trigger a cutscene where you see a woman calling out for help. Head to the building that has blue doors. Use the key that Sheva retrieved to enter the building. You will be treated to a shiny, new Ithaca M37 Shotgun, now you can deal with the girl in distress. Make your way up the stairs to trigger a cutscene. You will be attacked by the woman from the cutscene. After a minimal amount of damage, a parasite will spawn from her. However, it is possible to eliminate Allyson without revealing the parasite. Shooting her in the leg can set her up for either a neck breaker for Chris or a throat slit for Sheva. Neither method will reveal the parasite. Killing her with the Stun Rod or Rocket launcher also will not cause the parasite to emerge. Deal with the remaining enemies and head out via the back door. Follow your map to the indicated location.
Follow the linear path, until you reach a wooden ladder. When you're upstairs, follow the squared path until you reach a gap, jump across to find some treasure. Perform the partner action on the door, to trigger a cutscene. Ignore the deceased soldiers and take any items from the area. Continue moving down the corridor and take the elevator down.
Head down the passageway. You'll come to a door and past it are two ways to proceed. The door is locked so go down the passage. You will eventually reach a room with gas canisters. Approach the corpse to pick up the Furnace Key. While you are here, note the adjoining room, which appears to be the inside of a furnace. Also take note of the furnace control switch. Now backtrack your way to the indicated location to trigger a cutscene.
There are two ways to win this fight: by using the furnace or good old fashioned bullets (the latter is not advised for the first time but it will earn you a Gold Ring (5000)). After watching the cutscene, you will be treated to your very first boss battle in Resident Evil 5. Don't bother shooting the Uroboros, but instead fall back, and proceed out of the narrow hallway, and into the large room. You can, if you choose, begin by knocking down both gas canisters, and wait. (This can be done before you start the boss fight) As soon as the Uroboros enters the room, the shutter will close, sealing you inside. If you lure the Uroboros to one of the gas canisters, it will consume it (NOTE: do not waste these canisters by shooting them when Uroboros is NEAR them, the gas canisters are a pathetic waste this way, make sure the creature picks it up before shooting it). Lure the Uroboros to the furnace while it has hold of the canister, when it has just entered, shoot the canister and activate the controls immediately, which, if it stays in the furnace, should kill it, but the furnace will melt the Gold Ring.
Back track your way to the sealed door and use your key to open it and continue down the path. Stock up from the briefcase of handgun ammunition and take the elevator upward. After watching the cutscene, the chapter will come to an end. Hint: if the Uroboros is trying to get out of the furnace while the door is closing, shoot it with your shotgun to keep it in.