Then it becomes clear that a number of women have met their ends in London pubs. It seems a silent, secret killer is at work, striking in full view...and yet nobody has a clue how, or why - or where he'll attack next. The likeliest suspect seems to be a mental patient with a reason for killing. But knowing who the killer is and catching him are two very different propositions.
As their new team at the Peculiar Crimes Unit goes in search of a madman, the octogenarian detectives ready themselves for the pub crawl of a lifetime, and come face to face with their own mortality...