One night, Arthur Bryant witnesses a drunk middle-aged lady coming out of a pub in a London backstreet. 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...

One night, Arthur Bryant witnesses a drunk middle-aged lady coming out of a pub in a London backstreet. The next morning, she is found dead at the exact spot where their paths crossed. Even more disturbing, the pub has vanished. Bryant is convinced that he saw them as they were over a century before, but the elderly detective has already lost the funeral urn of an old friend. Could he be losing his mind as well?

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...