The Undoing, Series Finale, Sky Atlantic review - bluff and double-bluff as the truth is revealed

Throughout its preceding five episodes, The Undoing (Sky Atlantic) has skilfully, if a little shamelessly, kept the fickle finger of suspicion in perpetual motion.

Though Hugh Grant’s oily, untrustworthy oncologist Jonathan Fraser has been smack in the centre of the frame for the horrific murder of Elena Alves (Matilda De Angelis), perhaps that only meant that creator David E Kelly had been laying the groundwork for a spectacular reveal somewhere in this final hour.

The end of episode five had been startling enough, as Grace Fraser (Nicole Kidman) discovered the murder weapon (unless we were going to be confronted with more than one bloodstained sculptor’s hammer) hidden in the violin bag of her son Henry (Noah Jupe). Surely this meant Jonathan was guilty... unless Henry, who had witnessed his father’s blatant over-fondness for Mrs Alves and drawn his own conclusions, had been so horrified by his father’s family-shattering infidelity that he decided to eradicate the object of his extra-marital desires.

Apart from a disappointingly anticlimactic closing scene, this final episode was essentially a one-act courtroom drama which proved to be intense and gripping. If it was also a little bit melodramatic, the strength of the performances and the sheer pace of unravelling events made it easy to overlook the fact. It was gratifying to watch Jonathan’s defence lawyer, Hayley Fitzgerald (Noma Dumezweni, pictured below), finally having her day in court, because her performance has been a steely demonstration of cold logic and ruthless pragmatism.

Not to mention a willingness to tread boldly through ethical grey areas. When Henry admitted that he’d put the apparently murderous hammer through the dishwasher – twice – in order (he claimed) that it couldn’t incriminate his father, Hayley furrowed her brow and thought hard, before concluding that she could in good conscience refrain from handing in the hammer as evidence because it now had no evidentiary value. Which was just as well, since handing it over would mean “game over” for the defence.

You got the sense that only a very expensive lawyer would dare to stretch the envelope this far, so it was lucky that the deep pockets of Grace’s father Franklin (an excellent Donald Sutherland, criminally underused in this episode) were bankrolling the operation. More broadly, it was a shame that the theme of social disparity highlighted in earlier episodes, personified by the financial and material gulf between the Alves and Fraser families and lending a caustic twist to Jonathan’s infidelity, faded away as the series progressed.

As Jonathan’s trial unfolded, we were put through some violent mood-swings. The widowed Fernando Alves (Ismael Cruz Cordova), a fizzing ball of combustible emotions, lost control violently enough to remind us of his own credentials as a potential killer of his wife. Meanwhile Grant assumed the mantle of God-like rectitude as he reminded the court of his track record of saving children’s lives, and how he’d come to regard the Alves’s boy Miguel as his own son as he performed a miraculous cure on him. A killer? Moi? How could you contemplate such a thing?

The smartest twist was the way Grace’s career as a clinical psychologist became pivotal as the trial reached a climax. Her evidence on the stand was a play within-a-play as she sparred inscrutably with prosecutor Catherine Stamper (Sofie Gråbøl, not sounding at all Danish), and Kelley swished his matador’s cloak to keep us misdirected. But surely and steadily, it became clear how Grace's super-fine mind was working, that she had a cunning plan, and she knew which way the verdict would now surely go.

And needless to say, speculation is mounting about a second series...

• More TV reviews on theartsdesk