Things go from bad to worse when the officials finally realize the relic they have is a priceless artefact. Security is ramped up, and the heist team should let it go but Max begs Nick for help to pay back his debts.
So on the night of the heist, Nick is back in position, and Jack is back inside the Customs House working as the janitor in disguise. Jack makes an excuse, and gets into the server room, where he uses codes they bought from a systems administrator to switch off the CCTV cameras. He delays giving Nick the green light to enter the vault (possibly as he is busy securing another buyer online, or just to make him sweat, but we're never told) until finally Nick is told to proceed just as he is about to call it off.
The lead janitor spies a light in the server room and investigates. Jack overpowers him and locks the old man in a cupboard.
Meanwhile Nick is busy at work, first using cables to suspend himself from a cage above the safe that holds the priceless scepter, then drilling and dropping a depth charge inside which blows the safe door off it's hinges. He puts the scepter into a case and is about to make his escape when Jack shows up -
Nick is furious that the plan has changed, and it gets worse when Jack pulls out a gun. He tells Nick to give him the case, and remove his mask. The cameras will switch back on in a few seconds, so Nick has a choice to either put back on his mask and escape to the sewers, or chase after Jack.
The cameras switch back, the security guards sound the alarm, and Nick makes his escape (using a second level of tunnels for extra protection).
Jack makes his way out the front door in his disguise as the janitor, and away in a car to the bus depot. He is about to leave the city but can't resist a call to Nick to gloat and warn him not to try to come after him. Nick, escaping himself on a boat with his friend, asks him what he really has in the case. Jack opens it - to find the worthless metal prop they used in the dummy runs. Nick thanks him for taking the fall, now his face will be plastered all over the news, leaving Jack nowhere to go.
Max is watching the news that the heist work and they got away, and smiles to himself as he lights up. Nick meets Diane at the airport, and they make up.