After a new computer system is installed, mysterious financial losses start to appear in village Post Office tills. When the subpostmasters seek help, each are told that they are the only one having problems. Alan Bates, stubborn and computer-literate, refuses to put it behind him. When the Post Office goes on to accuse and harass subpostmasters for the shortfalls, Alan leads their fight back.

As the Justice for Subpostmasters Alliance (JFSA) grows in strength and numbers, Alan meets new allies and together, they take their cause to James Arbuthnot in Parliament, who persuades the Post Office they must investigate in earnest. Will investigator Bob Rutherford, hired by the Post Office, be convinced of the subpostmasters’ honesty?

Alan and the JFSA take their fight to the top of the Post Office, where CEO Paula Vennells offers them the chance to apply for compensation for their losses. Led by Post Office lifer Angela van den Bogerd, mediation proves slow and bureaucratic, and Alan seeks help from James Arbuthnot MP in holding the Post Office to account. For the first time in twelve long years, Alan begins to lose hope.

Alan leads the charge in persuading the JFSA to finally pursue the truth at any cost, against the might of the Post Office and its legal team--this time, in the highest court in the land. Can they come up with the evidence needed to persuade the Judge to side with them over a government-owned and much-loved national institution? Will a whistleblower be enough to get them over the line?