"Whispers Under Ground" is the third book in Ben Aaronovitch's Rivers of London series, which combines urban fantasy with police procedural elements. The narrative follows Peter Grant, a young constable who becomes involved in magical investigations. In this installment, Peter is tasked with uncovering a mysterious death that occurs in the London Underground, an investigation that leads him into the depths of the city's magical underbelly.
The story explores the interplay between the mundane world and the supernatural, featuring a variety of magical beings and their influence on London’s history and culture. As Peter navigates this complex landscape, he interacts with familiar characters from earlier books and faces new challenges, including the secrets that lurk beneath the city.