Νέα Υόρκη, 1985. Η Αμερική έχει επιστρέψει νικήτρια από το Βιετνάμ, έχει πρόεδρο τον Ρίτσαρντ Νίξον και βρίσκεται στα πρόθυρα πυρηνικού πολέμου με τη Σοβιετική Ένωση. Όλοι οι παλιοί υπερήρωες έχουν διά νόμου αποσυρθεί, όταν όμως ένας από αυτούς δολοφονείται, ο μασκοφόρος ντετέκτιβ Ρόρσαχ πιστεύει ότι αυτή είναι η αρχή μιας τεράστιας, πολύ επικίνδυνης πλεκτάνης.

Struggling to get home to her stranded baby, a young mother in Amsterdam receives an emergency alert on her phone: a nuclear missile has been launched at the city and residents have forty-five minutes to evacuate.

With the Doomsday Clock the closest it's ever been to midnight, Jane Corbin investigates the proliferation of nuclear weapons across the globe. She visits Los Alamos, home to the United States’ nuclear weapons development facility and the historic home of Oppenheimer’s Manhattan Project. In Scotland, she reveals the strategy behind Britain’s nuclear deterrent, and speaks to campaigners in Suffolk fighting against US weapons they fear will be based on UK soil. Jane also discovers how many of the global agreements and safeguards that have constrained the spread of nuclear weapons since the 1970s are breaking down. This is a story told by the scientists, investigators and diplomats who set the clock and have fought to ensure that the ultimate deterrent has not been used in over 70 years.