You start off in the mansion with Barry and Wesker. You are told to investigate a shooting you hear. After the cutscene finishes:
Go to the room on the left, the dining room.
There, Barry sees blood stained on the ground. After this cutscene:
Go to the door next to the fireplace, into the hallway. Take a left and watch the cutscene.
You can't kill this zombie, so:
Run back to the dining hall room.
Jill will run in and shout at Barry. Barry will shoot the zombie several times until it is downed. You are now told to report to Wesker. However, as you leave the room, you hear a door close. The zombie isn't there anymore! Anyway:
Go back to the main hall, where you first came in.
Wesker isn't there. After the cutscene, search for him and:
Run around the lower stair area and return to the base of the stairs.
A cutscene will play and Jill will be given a lockpick by Barry. This is a key difference that sets Jill apart from Chris. While Jill can open certain doors with a lockpick, Chris has to find old keys in his mission. After the cutscene:
Go to the same place where you met you first zombie.
Surprise, he isn't there anymore! He actually moved, so he's on the right side of the hallway, not the left.
Pick up Kenneth's video from the body and move through the door into the next room.
In this room, there are crows and some herbs on the ground. While tempting to do so, do not pick up all the herbs. Pick up one, because you will probably get bitten on the next part.
After picking up a herb, go up the stairs to the upstairs room.
In this room, you'll hear moaning, more herbs and spot a body on the ground. There are one or two zombies here, depending on your difficulty.
Make a right and avoid the zombie. When you come across a shiny object on the screen, pick it up. It's an arrow. Go to your item screen and examine it to break off the shaft. Afterward, take the right, unlocked door at the end.
If you haven't noticed already this room is directly above the dining hall. What you want to do is grab the defense dagger to your left. Afterwards, you want to run to the side, push the statue and knock it down to the dining hall floor. There is a zombie in this room so be careful. To figure out where he is, just press the aim button and your character will automatically spot the zombie.
Get out of this room by going through the double doors.
Look familiar? You've gotten yourself back to the central room on the second floor. You need to get outside though, not through the front.
Take the stairs down and go through the doors in the painting.
Outside is the graveyard and a few zombies. Don't fret, this place isn't too bad. Anyway:
Run down the stairs and go straight until you find a statue with an arrow missing. Place the arrowhead into the statue and head down the stairs.
At the end of the stairs is a firelit room with lots of gears. You'll also spot a coffin, suspended by four chains. You'll get to see what's inside when you get four masks later on. For now:
Get the Book of Curse, examine it and get the Mansion Key.