Based on the extraordinary true story of Alec Jeffreys' discovery of DNA fingerprinting and its first use by Detective Chief Superintendent David Baker in catching a double murderer.

David Threlfall, John Simm, Anna Madeley, Andrew Tiernan, Lorcan Cranitch, Dorothy Atkinson, Neil Edmond, Hannah Walters, Ged Simmons, Lydia Rose Bewley, Jaz Deol, Adam Nagaitis, Robert Glenister, Siobhan Redmond, Zara White, Esther Coles, Rakie Ayola, Paul Copley, Jessica Hargreaves, Tobias Burton-Rudge, Paul Lancaster, Katie Lightfoot, Becci Gemmell, Emma Lundy, Farzana Dua Elahe