The first book in the Cormoran Strike detective novel series was published in 2013 by a previously unknown author, Robert Galbraith. But in short order it became known that this was a pen name of J.K. Rowling, she of the Harry Potter books. Strike is a detective of the old school: roughhewn and flawed, burdened by a troubled past and a shaky present, aided by a sidekick – a woman as it happens – who is the personification of normality. The BBC has now adapted the first three Strike books as a television series called “Strike,” and it’s as sprightly and compelling as it sounds.

Cormoran Strike, the illegitimate son of an ageing rock star, is a former outstanding soldier who lost a leg in Afghanistan and is now a lusterless fellow who’s just broken up with his tempestuous fiancée. So dire is his economic situation that he sleeps on a folding army bed in his office. In the first book adapted for the series, “The Cuckoo’s Calling,” a modicum of salvation arrives when a temporary secretary, Robin, enters his life, and a new client, a former acquaintance named John Bristow, asks him investigate the death of his adoptive sister.

Lula, a beautiful model, rich, famous and with mental disorders in her past, has been found dead on the sidewalk below her penthouse apartment. A police investigation finds that she committed suicide, but the family, and in its wake, Strike, suspect murder. Everyone in her milieu seems to have a motive or is apparently lying. Was Lula murdered? And could the perpetrator have been her partner? An insistent suitor? A close girlfriend?

Like Sherlock Holmes and Doctor Watson, who were also given a thrilling reprisal by the BBC, Strike and Robin conquer London’s gray streets along with television viewers thirsting for a diversion.