Maxine Peake is Martha Costello, in her thirties, single, passionate and a defence barrister applying for silk. Innocent until proven guilty are four words she lives by. But how does this fundamental principle stand up to examination by clients who are sometimes good, sometimes bad and sometimes evil?
Martha is faced with challenging cases and surprising clients. Her beliefs and prejudices, her conscience and her faith in the criminal justice system are tested to the limit over the course of the series.
Joining Martha is Clive Reader, played by Rupert Penry-Jones. He's funny, gifted and dangerous. The same age as Martha, they're called to the bar together. Both are applying for silk – how they perform in court is vital to this process and Clive knows how to play the game.
Neil Stuke plays Billy, the senior clerk at Martha's chambers. He is dedicated to Martha, even if secretly he believes that she hasn't got a chance of being made a QC.
Nick Slade, played by Tom Hughes is Martha's pupil. Niamh Cranitch (Natalie Dormer) is assigned to Clive. Both are thrown in at the deep end and, as "baby barristers", must sink or swim. Only one pupil will be taken on as a member of chambers at the end of the series. Who will it be and why? And how will Martha and Clive influence the outcome?
Having just won an important case, Martha is given two new cases for the next day, with a chance of getting a good reference for her Silk application. Under huge time pressure, Martha has to prepare overnight. But will she be able to satisfy both the personal and the professional demands placed on her? Or will she be forced to sacrifice one case in order to win the other?
In an effort to boost her Silk application, Martha accepts a rape case, against her better judgement. Even worse, Clive is prosecuting her client and delights in riling Martha. As the case draws to a close, Martha begins to realise that things are not always black and white, especially when she makes a startling discovery.
Martha defends a vulnerable teenager and the pupils are given their first opportunity to stand up in court, taking on a low-level magistrates' court case. However, as the cases progress, both Martha and Nick find themselves in challenging positions. Can Martha save her client without endangering not only her silk application, but also her career?
Martha is forced to defend a police officer accused of racism at the police tribunal, at the same time as trying to get bail for another client. In the meantime, pressure increases on the pupils as the tenancy deadline draws near. And Clive receives some astonishing news which could change not only his personal life, but life at chambers for everyone.
Martha prosecutes a teacher accused of assaulting a pupil, but believes he is on too serious a charge and is not being properly defended by her colleague, Noah. Meanwhile, Nick takes on his first major case, and both Martha and Clive have their Silk interviews. Will Martha be able to ensure a fair trial for the teacher at the same time as succeeding in her interview?
Martha takes on the biggest case of her life, defending Mark Draper, a repeat offender on a murder charge at the Old Bailey. However, when the case starts to fall apart, Martha must try to remain focused on the trial as both personal and private pressures escalate. Meanwhile, it is decision time for the pupils, and the fate of chambers hangs in the balance.