| Lying, cheating, thieving—they’re the best undercover cops in the business. Liam Ketman (Nick Berry, Heartbeat) and Garth O'Hanlon (Stephen Tompkinson, Wild at Heart) take on false identities to infiltrate society’s underbelly and stop crime at its core. As they put their lives on the line, Liam tries desperately to hold his marriage together, while Gareth keeps his personal life a mystery. |
| Name | Character | Episodes |
|---|---|---|
| Stephen Tompkinson | Garth O'Hanlon | 22 |
| Nick Berry | Liam Ketman | 22 |
| Fiona Allen | Dr. Sophie Masterson | 16 |
| Lisa Maxwell | Pamela Ketman | 14 |
| Meera Syal | Marta Drusic | 6 |
| Ian McShane | Jamie Lamb | 2 |
| Andrew Woodall | Fraser | 2 |
| David Schofield | Vincent Hunter | 2 |
| Michelle Fairley | Phoebe | 2 |
| Con O'Neill | Terry | 2 |
| Peter Vaughan | Clayton Waddington | 2 |
| Peter Capaldi | Jeremy Church | 2 |
| John Standing | Ritchie | 2 |
| Brian Bovell | Brigstock | 2 |
| Francis Magee | Ronnie Sharkey | 2 |
| Michael Maloney | Dr. Gabriel Winterbourne | 2 |
| Lucy Cohu | Elinor | 2 |
| Christopher Fairbank | Harbinson | 2 |
| Stephen Boxer | D.C.I. Copeland | 2 |
| Donald Sumpter | Keith Sullivan | 2 |
| Daniel Mays | Dave Street | 2 |
| David Ryall | Denver | 2 |
| Ewan Stewart | Neil Starkey | 2 |
| Lizzy McInnerny | Fiona | 2 |
| Jake Wood | Rio | 2 |
| Nicholas Gleaves | Bradley Sullivan | 2 |
| Richard Hope | Dr. Kingswood | 2 |
| Yasmin Bannerman | Toni Carr | 2 |
| Ralph Ineson | Craig | 1 |
| Jonny Coyne | Customer(as Jonathan Coyne) | 1 |