Monochrome is a busted flush - an inquiry into the misdeeds of the intelligence services, established by a vindictive prime minister but rendered toothless by a wily chief spook. For years it has ground away uselessly, interviewing witnesses with nothing to offer, producing a report with nothing to say, while the civil servants at its helm see their careers disappearing into a black hole.

And then the OTIS file falls into their hands.

What secrets does this hold that see a long-redundant spook being chased through Devon's green lanes in the dark? What happened in a newly reunified Berlin that someone is desperate to keep under wraps? And who will win the battle for the soul of the secret service - or was that decided a long time ago?

Spies and pen-pushers, politicians and PAs, high-flyers, time-servers and burn-outs ... They all have jobs to do in the daylight.

But what they do in the secret hours reveals who they really are.