The bank to which Langdon and Sophie were led is a state-of-the-art Swiss bank, which specializes in anonymous safe-deposit boxes.
Anyone can store anything completely secretly…for the right amount of moolah, that is.
Their key opens the two gates leading into the parking garage. So far, so good.
When they finally get into the bank itself, they show their key to the concierge-type dude, who immediately directs them to the elevator and alerts someone that they're on their way.
Langdon and Sophie assume it's just his great sense of hospitality. In reality, the concierge-dude/guard called his manager to tell him that the fugitives the French police are tracking had just arrived. Oops.
They exit the elevator to a warm welcome from an older host, who reassures them that sometimes keys are inherited, so it's not unusual to get people who are a bit bewildered by their protocol.
He informs them that for gold key accounts, the minimum safety-deposit box lease is for fifty years. Paid in advance.
He says they just need to insert their key, punch in their account number, and then their box will appear via robot, and they'll have all the time they need to go through it without interruptions.
Umm, hold up there, cowboy. Account number?
Their host gets a phone call that makes him frown, and then he leaves them.
Meanwhile, Fache calls Collet to tell him that Langdon and Sophie are at the bank. Go get 'em.