Melbourne, 1868. When dazzling theatre star Marie St Denis dies in the arms of her best friend, fellow actress Lola Sanchez, everyone believes it was suicide by laudanum overdose. Everyone except Lola. On the brink of stardom herself, she risks everything by embarking on a quest to find Marie's killer.

When journalist Magnus Scott, writing as 'the Walking Gentleman', publishes a compassionate obituary about her friend, Lola decides to seek his help. A fraught attraction develops between these two amateur detectives from opposite sides of society, and their volatile relationship soon begins to compromise their investigation.

Lola keeps a secret from Magnus. She traverses the corrupt underbelly of the brash young metropolis just as he does, but disguised as a boy, entering dangerous, forbidden spaces where the lives of the rich and privileged intersect with the city's underclass and outsiders: bohemians, theatre folk, prostitutes, down-and-outs and opium addicts.

Neither are prepared for the truths they will uncover about the powers that rule Melbourne - or the consequences for their own lives. And now they must race to find the murderer before the city destroys them both.