The last chapter is the shortest one in the whole game but you shouldn't expect that is the easiest one. Just the opposite, is the hardest and the most challenging. When I was playing it I died many times, a split second can kill you. During this episode you will not find any secrets or special tasks for Brothers.
The shooting will start from the very beginning of the gameplay [!]. Hide as fast as you can behind a nearby sarcophagus and start to eliminate you opponents. Do not rush because you can die in the blink of an eye.
After killing first opponents a short scene will be automatically triggered and the whole room will start to cover with sand. From that moment you should hurry. There will be a lot of enemies and some of them upstairs so keep an eye on them.
In one moment you will get a new task - kill Barnsby. In order to do that, take the nearby stairs which are next to your brother (the other one are partly destroyed).
At the top you will encounter Marsie and many opponents. When you will try to get to her, rocks from the ceiling will cut your way. From that moment the final battle of the game will start [!]. Opponents will strike in two waves (without those at the beginning). During the fight do not rush and try to stay alive. That's why stay all the time behind the cover. When your Concentrate Mode will be fully charged wait 'till another wave of opponents will attack you.
You will be able to make out Barnsby but do not shot him until his gang won't be in charge. When all other opponents die a short conversation and a duel will be triggered. Win and finish the game.