Holmes returns angry and disturbed after a visit to Hammersmith mortuary at the end of a particularly tiresome case. Whilst at the mortuary, Lestrade shows him the body of a young woman who has taken not only her own life, but that of her unborn child.
So begins a tale that highlights the exploitation of vulnerable women through quack medicine and blackmail in a scheme of unbelievable proportions. Julia Moriarty, the sister of the late Professor James Moriarty is suspected to have a hand in the affair and Holmes must involve Lestrade in a bid to apprehend the perpetrators. Lestrade springs the trap but in doing so, causes Watson to be grievously wounded.
Moriarty escapes but has she revealed to Holmes her Achilles heel? Whilst Holmes has seen that the 'Rule of Law' is maintained and the case concluded, Watson is in turmoil as he is unsure whether their investigation has inadvertently caused further harm to those they sought to protect.