There once was a city so corrupt and filled with violence and crime that the government chose to build a great wall isolating it from the rest of the world. However, there were some who changed and believed they didn't belong there. So they joined together to form an organization, lead by ex-Sheriff William Dorado, determined to find redemption, a way out, or the legendary key to unlock the Iron Gate.

Mark Wahlberg as William Dorado - Once a county sherriff, now the founder and leader of the Brotherhood of the Iron Gate, Will has dedicated his life to fighting the countless crime and gangs within the city walls while relentlessly searching for the mythical Key to the Iron Gate.

Jennifer Love Hewitt as Christina Bradley - Born within the city walls, orphaned by the parents she never knew, Christina is a sexy cocktail waitress searching for answers to the many questions surrounding the story of her mysterious birth. She comes to Detective Wisely for answers and Mick believes he may be on to something. He sends Will who reluctantly checks in at her cocktail bar and immediately realizes this is Espiransa's daughter. Mick recalls her to his office and the two slowly unravel her past.

Colin Farrel as Mick Wisely - He is the city's most renowned detective and also serves the Brotherhood undercover. He had heard tales of the key and when young Christina stumbles into his office pleading for help he feels he is on to something.

Salma Hayek (body doubled by Vida Guerra) as Bella Scaranato - The only female member of the Brotherhood, Bella decides to take matters into her own hands and attempts to seduce Baron Grimely. She thinks she has succeeded until the next morning she finds herself chained to a stone table. She is severely beaten and enprisoned within the Wall. Here, she meets Espiransa, who knows the Wall and all its passageways quite well, having been enprisoned there for quite some time. The two work together to eventually escape the Wall and later help the Brotherhood navigate it.

Sean Penn as Baron Erik Grimely - The appointed ruler of the walled realm, he spends most of his time within a heavily guarded domain inside the Wall from where he watches over the land and occasionally attends meetings with its inhabitants. He is known for his cruelty towards those who disobey him or try to escape the city walls.

Bruce Willis as Skiffer - The most notorious crime boss the world has ever known, Skiffer resides within the city walls where he controls and/or oversees every illegal operation that takes place. He is constantly after the key, believing it belongs to Espiransa. When Baron Grimely hears of his operations towards finding the key, he ransacks his lair and retrieves Espiransa. However, upon hearing of Christina, Skiffer dispatches an entire army of bounty hunters to locate and capture her.

Maria Cucinotta as Espiransa Bradley
Christina's mother, at the start of the film is seen emerge from her shower as Will intrudes to inquire of the key and warn that Skiffer and his gang are coming to retrieve the key. As Espiransa slips on some lingerie, Will sees Skiffer threw her balcony. He waits until they have seized her then pursues their limosine on his Cloudscraper. He follows them aboard a train where he is beat down by Skiffer's henchmen and cast into a river, taken for dead. Skiffer's men dare not hurt her knowing she is their only way of finding the key. So, she is simply questioned tirelessly and subject to Skiffer's mind games. When Skiffer's lair is ransacked by the Gate Keepers, Espiransa is taken and enprisoned within the wall. She remains there for several years, until she is joined by Bella and the two formulate a plan to escape.