The Hanging Tree was the Tyburn gallows which stood where Marble Arch stands today. Oxford Street was the last trip of the condemned. Some things don't change. The place has a bloody and haunted legacy and now blood has returned to the empty Mayfair mansions of the world's super-rich. And blood mixed with magic is a job for Peter Grant.
Peter Grant is back as are Nightingale et al. at the Folly and the various river gods, ghosts and spirits who attach themselves to England's last wizard and the Met's reluctant investigator of all things supernatural.