Case Histories, BBC One

He's back - and he's even moodier than before. Jackson Brodie, the private dick for whom the word “brooding” was invented, hasn't been seen on BBC One since 2011, and now there are three 90-minute films to feast on, based on Kate Atkinson's novels and relocated to Edinburgh. Last night's was Started Early, Took My Dog.

The story started in Munich, where Brodie (Jason Isaacs) was involved in a child snatch that he was doing solely for the money, as he had just spent two months visiting his daughter Marlee, who now lives with her mother in New Zealand, and that costs. It all went wrong as his dodgy accomplice was killed and Brodie narrowly escaped a bullet himself as the child's nanny fought back. He had been duped - the girl was returned to her father, not her mother, as he had been told when he took on the job - and Brodie's guilt at taking a child away from its mother (he has childhood ishoos, you see) was the thread running through last night's story.

It picked up where the last series left off. Brodie's ex-girlfriend Louise (Amanda Abbington) is now engaged to another bloke and he received an invitation to their wedding (cue more Brodie brooding). The fiancé is boring but dependable, and not a commitment-phobe like him. Louise is still a detective inspector for the police in Edinburgh so their paths cross, and when they met at a crime scene connected to his latest case, she said “why do you always have to complicate things?”, which could be a description of his life in general, and not just his line of work.

His case involved Hope (Emma Hamilton), an adoptee looking for her birth parents, and Brodie uncovered some murky history, both about her mother – she was, he discovered, what used to be called “a good-time girl” - and a police cover-up surrounding a prostitute's death in 1979 (Maurice Roëves giving good nasty as the cop, now old and frail but back then a right piece of work). Victoria Wood (pictured right) played Tracy, once an Edinburgh police officer involved in that investigation, now a security guard in a shopping mall. Like Brodie, she's riven with guilt – in her case about the prostitute's toddler son Michael, a child she feels she abandoned to his fate – and when she did something in a moment of madness involving another prostitute's child, Brodie had to decide whether to tell the authorities or help her escape them.

Of course we knew what he'd do because Atkinson's skill as a novelist is to create a believable emotional hinterland to her characters, and we know behind Brodie's curmudgeonly exterior lies a softy, albeit one whose motivations are often a mystery even to him. Pete Harness's sure-handed adaptation (directed by Kenny Glenaan) was true to that, and gave the story narrative drive as he introduced a few red herrings while jettisoning extraneous characters - although he kept Ambassador the dog to good effect.

However, while I'm not particularly dense and I love a good detective story, I lost the plot somewhere and couldn't work out the crucial link between Hope and Michael's stories as Brodie tied up the case. Perhaps I was too busy taking in the views of Edinburgh, surely these islands' most beautiful city and used to great effect here, and so missed a crucial line. But Atkinson has created a great character in Brodie and Isaacs realises him perfectly. Add in superb support from Abbington and Zawe Ashton as his long-suffering assistant, plus a liberal dose of humour, and what you get is great Sunday night television.