Cue probably one of the best intros for a game you'll ever see. After this you'll end up on the landing of your mansion. First turn around and take out the assassin coming in behind you (those movie buffs will remember this guy is the one that killed Tony in the movie). Now shake to enter Blind Rage mode and rush downstairs killing everybody in your path and head to the left. Hopefully you'll get to the room before you run out of blind rage so you'll clear it out as well. If not, then enter the room and take out the guys on either side of the room and behind the pool table. Don't forget to taunt them each time you kill somebody to get more balls and to raise your rage meter. Now keep going to the right from the pool table, and this will trigger a cut scene where a henchman will reveal a hidden passage.
Enter the passage and take the health kit if needed and go down. After the second corner there should be somebody waiting, so take him out with ease. Keep going down and you'll reach a fork, take out the guys coming after you first and then head left to take out the guy in the room and keep going down the previous path, which will explode. Now go left and take out the guys in the next room, go right and then shoot the guys coming through the doorway and don't forget the guy that's right at the end of this room down a ditch of sorts. Go through the doorway taking out the few guys that remain in your way and up the stairs.