| Name | Character | Episodes |
|---|---|---|
| David Tennant | Dennis Nilsen | 3 |
| Jason Watkins | Brian Masters | 3 |
| Jay Simpson | DS Chris Healey | 3 |
| Ron Cook | DSI Chambers | 3 |
| Joel Morris | Tim Wells | 3 |
| Daniel Mays | DCI Peter Jay | 3 |
| Ben Bailey Smith | DC Brian Lodge | 3 |
| Barry Ward | DI Steve McCusker | 3 |
| Faye McKeever | Linda Jay | 3 |
| Laurie Kynaston | Carl Stottor | 3 |
| Alexander Bhat | DS Jones | 3 |
| Bronagh Waugh | Charlotte Proctor | 3 |
| Oscar Salem | Juan | 2 |
| Jonathan Coy | Professor David Bowen | 2 |
| Neil Edmond | Clerk of the Court | 2 |
| Pip Torrens | Ivan Lawrence QC | 1 |
| Andrew Woodall | Dr Hardy | 1 |
| Ross Anderson | Douglas Stewart | 1 |
| Gerard Horan | Commander Gerald Lookwood | 1 |
| Chanel Cresswell | Lesley Mead | 1 |
| Beth Goddard | Frances | 1 |
| Tony Way | Mike Cattran | 1 |
| Pauline Turner | Elizabeth Sinclair | 1 |
| Stuart McQuarrie | Ronald Moss | 1 |
| Amaka Okafor | Emily | 1 |
| Silas Carson | Russell Cavendish | 1 |