"The child can never be fully human. But after Clarabelle drinks this, at least, it shall be mostly human. [...] And for that, we need your blood."
Dr. Vaughan claims that your human blood can help make sure that Clarabelle's "offspring" will be mostly human.
[Find the rest of the story at http://www.fallenlondon.com]
Unlocked with Ambition: Light Fingers! exactly 120
Storylet appears in Castles in the Ceiling