As London's only female detective, Eliza is struggling to get work. Desperate for money, she 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 pleaded guilty.
Eliza is hired by the man's wife to save him from the hangman's noose but, along the way, Eliza clashes with Duke who is inundated with other crimes.
Relying on his instincts as a veteran copper, he sees this as an open and shut case, so why rock the boat when there are more deserving investigations to pursue?
With her father's business on the line, can Miss Scarlet unravel this perplexing mystery and win the Duke's respect along the way?