Robert Jekyll, grandson of the original Doctor Jekyll, is summoned to London to discover his dark ancestry, but the naive young doctor's arrival draws the attention of more sinister forces.

Robert cannot understand how he survived the attempt on his life, and follows the advice of new friends Lily and Max to seek answers in his grandfather's house.

After Garson tells Robert that his ancestors unleashed their dual identities with a form of medication, Robert is determined to cure himself the same way.

Wracked with guilt after failing to get to his grandmother before Captain Dance's men, he works tirelessly to cure her of sepsis. Garson discovers that Hyde's blood has antibiotic properties.

Robert visits a distant branch of his family in the country. But, when he and Max learn that a series of murders have occurred in the village, they suspect Tenebrae.

As Robert grieves for his friend, a Ripper stalks London. With the hysteria impacting Bella's business, Hyde joins Spring-Heeled Jack to pursue the killer, discovering a monstrous parasite is to blame