Martha Costello is now a QC, but she learns fast that it can be lonely at the top. At Shoe Lane Chambers times are tough, and senior clerk Billy struggles to keep things afloat while Clive Reader tries to be stoic about his unsuccessful silk application. Martha is defending Brendan Kay, a member of one of London's biggest crime outfits. He is accused of blinding a man, who allegedly disrespected their 'number two'. Martha's job is made harder because Brendan's solicitor, Micky Joy, is an old school player of the system who walks both sides of the line. Also up against a notorious QC, Caroline Warwick, nicknamed Lady MacBeth for her uncompromising approach in court, Martha feels herself pulled by the various political forces around her, and realises to win she will need an all or nothing defence. Meanwhile, Clive takes on a sensitive case with a new solicitor, George Duggan.

Martha represents Captain Ed Ryan in a court-martial. He is accused of disobeying an order, resulting in the death of a 19-year-old private. Under the watchful eyes of a distraught family who want answers, Martha navigates the army's legal system with the help of Captain Cassidy, Ryan's unit defence officer. Doggedly seeking the truth, Martha slowly peels back the layers of past and present wounds, revealing the shocking reality of modern combat. Meanwhile, temptation is never far away for Clive, who is warned by Billy to keep his relationship with George Duggan purely professional.

Clive is in Oxford, prosecuting three students accused of sexually assaulting a waitress. Up against an intimidating defence counsel, Clive begins to waver, but a chance encounter with an old friend helps him discover a passion for prosecuting he did not know he had. When the case is in danger of collapsing, Clive is faced with one of the biggest decisions of his career. Meanwhile, Martha is defending Ricky Armitage, who trashed his local mini-mart and attacked the shopkeeper. His level of violence and lack of remorse is astounding, yet Martha tries to divert the self-destructive path that Ricky was fated to walk.

Martha finds herself in a David and Goliath battle when she represents the driver of a high security prison van. When some of his prisoners escaped, Michael Ward opened the doors of his van to find another dead. With Ward and the security firm accused of causing the prisoner's death, Martha fights to make Ward stand up for himself, lest he becomes the fall guy. Chambers take on a new pupil, Daniel Lomas, who helps Martha unlock her client. Meanwhile Clive is struggling to get through to Fatima Ali, and Billy, still feeling the pressure from Micky, starts to uncover hidden truths about CW

At the Supreme Court, Martha is representing Jackson Henderson in a death row case. Against a ticking clock and with Billy breathing down her neck, Martha faces the toughest legal argument of her career. Clive increasingly feels that he is not the right barrister for Fatima Ali and, at the risk of losing George, persuades Martha to take the brief, conveniently leaving him free to prosecute Jody Farr. Martha knows unless Fatima speaks up for herself, the truth will not surface. Just as she thinks the case is lost, Martha is offered a deal with the devil in return for Fatima's freedom.

Reluctantly representing Jody Farr, Martha vows to do her job, but she will not allow him or Micky to get under her skin. Fighting shifting power plays and an untenable defence, she begins to feel that Jody is not getting a fair trial and suspects foul play. Setting a dangerous trap, can Martha uncover the unbelievable truth? With the date of his tribunal looming, Clive focuses all his efforts on prosecuting Jody Farr, despite the apparent lack of support from CW. In the face of an uncertain future, Billy finds himself trapped by Micky Joy and loyalties are stretched to breaking point.

Clive who has now become a QC is celebrating with friends and colleagues but the party is interrupted when Alan's son is arrested on suspicion of the murder of a policeman, while Martha hits the bottle after an Inspector lies in court to frame her client.

Martha defends a footballer accused of attacking an opposing player during a match.

Martha is approached by a euthanasia campaigner to defend a friend, who helped her paraplegic daughter to take her own life.

Martha goes into prison to visit an ex-lover who is accused of shooting dead gang leader Jimmy Monk, who demanded protection money for him to open a night club.

Clive is forced to withdraw from the case, convinced of Sean McBride's guilt. Billy tries to help Martha by convincing Micky Joy to give evidence on police corruption. Harriet and Clive consummate their relationship.

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?

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?

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 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 is asked to help a solicitor whose nephew is wanted for extradition by the American authorities in relation to a bomb attack at an Arizona university.

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.