Contains spoilers

BBC FOUR gave a fifth outing to Peter Haber’s Beck this Saturday. The Hospital Murders was an utterly atypical addition to the Beck stable and may have confused those familiar with the legendary novels of Sjöwall and Wahlöö. In a way it is a cautionary tale about the incomplete importing of long serials – for although for Brits The Hospital Murders was episode number 5, for large parts of Europe it was episode 30. But the episode was really a farewell to the actor Mikael Persbrandt, for whom this is the last full outing after 18 years playing hardman Gunvald Larsson.

Is it the right time for Persbrandt to go? Eighteen years in a role is quite a stint. Larsson has been at times quite two-dimensional: ready to lash out at undesirables, and the antithesis of a good team player. But since 1997 we have seen both Larsson and Beck develop as characters beyond the imaginations of their original creators. And Persbrandt is not completely lost to action films: he will make another outing as Hamilton – a kind of Swedish James Bond.

But in The Hospital Murders Larsson is clearly no longer at the peak of his physical powers. His impeccable dress sense seems to have deserted him, and he needs glasses. Beck, who has had one or two minor (and usually plot-related) dalliances since his divorce, has to decide whether to accept a married colleague’s advances. The not-very-interesting plot revolves around infidelity and Beck is able to view his options through the lens of the resulting chaos. For once, the crime is secondary and character is all.

It isn’t clear whether we will see Larsson again at all. The producers say only that the way in which he leaves ‘will feature’ in the next film. But it would be fitting if the final scene of The Hospital Murders, beautifully acted (and reminiscent of the ending of Withnail and I), were our last sight of the brilliant and flawed detective. For those of us who have had the chance to delight in Gunvald’s somewhat binary nature, the send off is apt and done in a rather classy and not schmaltzy way. For those for whom The Hospital Murders was episode 5, this is your invitation to find what went before.

Find all our Beck coverage here.