‘You can’t win trying to save people like me – you have to go big. Walk away from me now, stay brave, be strong, hold your dignity. Go big!’ So Rudy Jones (Dennis Haysbert) tells barrister Maya Cobbina (Sophie Okonedo) shortly before facing execution by lethal injection in the US. Outside the Louisiana Detention and Correctional Facility, Maya tells Rudy’s supporters: ‘The anger that I feel will not be softened until they stop killing brothers and sisters and calling it justice.’

The powerful opening to Peter Moffat’s prime-time Sunday night drama is sustained as Maya drives away with the radio station blaring that Rudy would have a ‘humane and painless death, which is more than can be said for the agony he inflicted on the esteemed public servant he so brutally murdered’.

Then we learn that Rudy is in fact still alive and Maya, suppressing the emotional strain of representing a client for a long time, pleads with Judge Kramer to consider a stay of execution. Back in the facility, she tells assistant attorney general Livermore that the ‘eighth amendment prohibits cruel and unusual punishment’. Now the gritty dialogue gives way to unsettling scenes in the execution room, where a drill is used on Rudy’s body to speed up his death. ‘It’s botched, he’s alive, he’s in terrible pain,’ Maya screams down the phone.

The next time we see Rudy he is still alive and being tended by a doctor, a testament to Maya’s professional concern for her client. Even when a juggernaut whistles past after she pulls up in a dangerous spot on the road to take a call on her mobile, nothing distracts her.

Back in her London chambers, Rudy’s comment about going ‘big’ is echoed by Jimmy (Phil Davis), as they discuss her being considered for the role of director of public prosecutions. New evidence has emerged in a high-profile sensitive case and it is clear that the DPP would have a big say.

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But as Maya agrees to to be interviewed for the position, it is clear that not everyone is thrilled by the news, as it potentially puts her husband Nick Johnson (Adrian Lester) in a tricky position. Unbeknown to his wife of 20 years, Nick is an undercover police officer. And with Maya being linked to the DPP position, this has clearly rattled Nick’s old employer. ‘There’s a perfect storm coming,’ Nick is warned by a sinister police presence. ‘We want you to share with us what she is thinking.’

So the smooth and quick-thinking Nick, played with aplomb by the excellent Lester, is facing a dilemma about how he can still maintain a happy family life with his children Clem, Dan and Ella while carrying out clandestine police work. Another secret is that Nick’s father is very ill; he even removes his wedding band when he visits him and later has to hide his grief from his family.

It is refreshing to see a barrister away from the formal milieu of court taking on brusque prison officers in a life-and-death situation. In fact, such is Maya’s emotional investment in her death row case she has what appears to be a seizure in a desolate field. Stirring drama that will grip you.

Nicholas Goodman is a sub-editor at the Law Society Gazette