We're back to the same location as in Scene 3, and Cobb is talking to some person named Mal. She asks if "the kids miss her" so she must be his ex-wife.
Then Cobb is shooting people with his silenced pistol as he makes his way toward Saito's safe to steal his information.
Just as he opens the safe and exchanges envelopes he is caught red handed by none other than Mal and Saito. It turns out she ratted on him.
Then the reveal: Everyone is in a dream.
Apparently this is Arthur's dream.
Cobb shoots Arthur to wake him up—you always wake up if you die in a dream. The dream starts to collapse (the walls of the building collapse, etc) but not before Cobb is able to read the confidential documents he's stolen.