Drama series. Displaying increasingly irrational behaviour but determined to prove his innocence, PS David Budd is desperate to get to the bottom of the conspiracy.

Determined to push the investigation forward, principal protection officer David Budd targets enemies of home secretary Julia Montague. As he delves into Julia's political manoeuvring before the attack, David's theories about a conspiracy at the heart of government look increasingly plausible.

But when concerns are raised about David's psychological health, and allegations about his professional conduct come to light, the finger suddenly points at him. Friendless in a high-stakes game, David realises too late that he himself could be a target.