In early 1970s London, a car dealer named Terry is presented with a seemingly foolproof plan to rob a bank. Contacted by his old flame, Martine, Terry is enticed by the prospect of a clean job with potentially huge rewards. Martine presents the bank heist as a simple smash-and-grab operation: they're to tunnel into the safe deposit box hall and help themselves to the cash and jewelry. Unbeknownst to Terry, Martine's motives are driven by a secret agenda – she's been coerced by an MI5 agent to retrieve a specific safe deposit box to avoid a major political scandal, implicating royal and government figures.

Organizing a band of amateur thieves, Terry takes the lead on the mission. They begin to dig a tunnel from a nearby shop to reach the bank’s vaults. As the crew works meticulously to avoid detection, their plan encounters several hitches and they must overcome a number of unexpected challenges. The heist initially moves forward according to plan, revealing that the bank’s security measures are not quite as robust as they should be. However, as they gain access to the treasure trove of safety deposit boxes, they find much more than they bargained for, and the ramifications of their discovery extend far beyond monetary gain. Their intrusion sets off a chain of events that entangles them with dangerous criminals and corrupt government officials, revealing that the job is far from ordinary or safe.