Is the health service facing up to a medical emergency that now kills more than any cancers and heart attacks? When Alistair Jackson's elderly mother died suddenly in her local hospital, he was told she had received the best care possible. It took him two years to uncover how the tell-tale signs of suspected sepsis were missed and how potentially life-saving antibiotics weren't administered for hours. After getting to the truth, he meets the families of some of the estimated 14,000 people whose deaths might have been prevented with better treatment and hears from the health professionals trying to tackle Britain's 'silent killer'. The film reveals how under-reporting of sepsis cases means the crisis is likely to be far deeper than thought. With exclusive access to NHS figures he discovers that despite high-profile improvement campaigns, people's chances of getting the best care can still depend on where they live - and goes back to his mother's hospital to ask if anything has changed.