Others seem to want a second series
http://www.ok.co.uk/tv/1141306/in-the-dark-season-2-bbc-helen-weeks-baby-who-is-dad-paul-adam-drama-new-series
. . . and Mark Billingham seems to be happy to write it:
>>> Billingham, who has won the Dagger for crime novel of the year twice, admits that a side-kick getting their own series is unusual unless the lead character dies, as with Lewis. But the BBC were looking for a strong female detective and Helen Weeks fits the mould.
"It's a series about Helen Weeks and if there is a second series, this will also be just about her," he says