Following the conviction of some of those involved in the theft and handling of the Brink's-Mat gold, the police realised that those criminals only ever had half of it. Series two explores what happened to the other half, and the criminal fortune it created. As the police investigation continues, it becomes a tense, high-stakes journey into international money laundering and organised crime, while the police embark on dramatic manhunts as they desperately try to solve the longest and most expensive investigation in the history of the Metropolitan Police.