One night, Arthur Bryant witnesses a drunken lady coming out of a pub. The next morning, she is found dead at the exact spot where their paths crossed. Even more disturbingly, the pub has vanished and the street has changed. Bryant is convinced that he saw them as they looked over a century before - is elderly detective losing his mind? Then it becomes clear that a number of women have met their ends in London pubs and the likeliest suspect seems to be a mental patient. 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...