After headstrong Eliza Scarlet inherits her father's detective agency, she is obliged to find a male business partner to operate in Victorian London.

Eliza takes a seemingly impossible case: proving the innocence of a man found at a murder scene with a bloodied knife in his hand, who has already pleaded guilty.

Eliza is hired to go undercover and infiltrate a potentially disruptive gang, but is less delighted when she learns she will be spying on a group of suffragettes campaigning for the vote.

Eliza is hired by a Death Photographer who is receiving bizarre and threatening messages from beyond the grave, and later makes a surprising discovery about her late father.

The final entry in Henry Scarlet's casebook takes Eliza and Duke to a seemingly abandoned prison on the outskirts of London.

Eliza pieces the puzzle together to find out what really happened to her father, while Duke looks past his prime suspect to investigate a surprising lead.