| Name | Character | Episodes |
|---|---|---|
| David Tennant | Alexander Litvinenko | 4 |
| Neil Maskell | Brent Hyatt | 4 |
| Margarita Levieva | Marina Litvinenko | 4 |
| Mark Bonnar | Clive Timmons | 4 |
| Daniel Ryan | DAC Peter Clarke | 4 |
| Barry Sloane | DS Jim Dawson | 4 |
| Greg Kolpakchi | Oscar Enrique | 4 |
| Sam Marks | DC Oliver Gadney | 4 |
| Radosław Kaim | Andrei Lugovoy | 4 |