Elise takes her boat straight to a secret police dock and gives herself up - she is an undercover British agent who has disappeared and gone rogue. She was tasked with getting close to Alexander Pearce, but instead she fell in love with him.
She tells Inspector John Acheson (Paul Bettany) that she is meant to meet Alexander at the Ball. She will go back undercover, and will wear a wire to trap him. Bettany is jealous that it is the tourist who has talked her round.
Frank decides not to take the first flight out of Venice, and instead gatecrashes the Ball to find Elise.
Elise is handed another mysterious letter stamped "AP" by the bad guy from A Knight's Tale - so he is Alexander Pearce and not a French agent! The letter gives her an address to get to. She tries to follow him, but Frank stands in her way, in the middle of the dancefloor. She dances with him, awkwardly (I don't know if that was meant to be on purpose or just bad acting) - and then to save his life, she breaks his heart.
She leaves, gets into a taxi boat, and off to meet AP. Frank is picked up by Interpol and taken to a police boat. At first Bettany has a little fun with him, and then tells him that he knows he is a nobody and has been used by Elise. To keep him out the way, he is chained to a chair and kept on board.
The Russians also get into a boat to follow Elise. Bettany follows them both.
Elise disembarks and enters the apartment to meet AP. Immediately she is joined by Reginald Shaw and the Russians. They hold a knife to her and demand to know where the safe is - at the last moment she spies a large marble disc on the wall with the two-faced Roman goddess in the fireplace - and tells Shaw to look inside.
He opens the facade to find the safe, protected by a number lock. Elise doesn't know the combination. Suddenly, Frank enters the apartment. Bettany is amazed - and looks to his empty soat.
The guns are turned on Frank. He tells Shaw that he is Alexander Pearce. Elise tells him not to do it. Shaw steps closer and questions the face, the hairline -- and the accent -- so Frank reverts to his Captain Sparrow 'British' accent. He offers a deal - if Elise released he will enter the combination. Instead Shaw grabs Elise and holds a gun to her. The snipers demand that a shot be taken - but Bettany tells them to stand down - he knows that Alexander will show. Frank gives in and walks to the safe, slowly. Elise whipsers "I love you" as he passes.
He is about to press the first number on the safe. Chief Inspector Jones (Timothy Dalton) enters the boat control room and over-rides Bettany, telling the snipers to open fire. The snipers gladly do so and in a well-timed move take out Shaw and the Russians together. Elise is relieved.
Timothy Dalton and the other officers enter the apartment. He tells Elise that her suspension is lifted ... and then that she is fired. She is relieved. Immediately word is in that they have their man -- they have Alexander Pearce.
They race down to the docks and have the bad dude from A Knight's Tale. He tells them that he expected to be arrested - and when he was taken to tell them that he is just a tourist, responding to text messages. He would receive money and texts from a man he has never met, telling him to turn up at various places.
Meanwhile back in the apartment -- Frank enters a very long number into the safe - and it opens. Inside are ledgers and what look like passports. I think it was meant to signify bonds, or they just couldn't find enough fake bundles of cash. Elise's jaw hits the floor. Then they kiss.
Dalton and Bettany return to the apartment. They blow the locked safe - and inside find a single cheque - for almost £800million signed Alexander Pearce. Bettany is confused. Dalton is happy that it's over and the bad guys are dead. He should wait to cash it first before he counts his chickens!
Out in the sea the next day Elise can't take her eyes off the new Alexander. She asks why he chose that face at a cost of £20million? ... but that she could get used to it.