The series ends with Ethan learning the shocking truth about Kaetenay, and Dr. Seward using hypnosis on Renfield. Meanwhile, the Creature must make a moral decision that could affect his relationship; and Sir Malcolm, Ethan, Kaetenay, Dr. Seward and Catriona fight to save Vanessa.
Ethan, Sir Malcolm and Kaetenay return to London, where Ethan searches for Dr. Frankenstein. Meanwhile, Dr. Seward discovers Renfield's secret; and Lily reveals a heartbreaking story from Brona Croft's past.
Vanessa turns to old friend Ferdinand Lyle for help, who introduces her to Catriona Hartdegen, a new ally. Meanwhile, Lily, Dorian and Justine put their plan in motion; and Ethan, Sir Malcolm and Hecate arrive at Jarod Talbot's ranch.
Season 3 begins with Ethan, now a prisoner under the watchful eye of Scotland Yard Inspector Rusk, on a train speeding through the desert of the American West. Meanwhile, Sir Malcolm is confronted by a mysterious Native American man in Zanzibar. Back in London, Dr. Frankenstein seeks out his old friend Dr. Jekyll; and Vanessa seeks the help of Dr. Seward to battle a new evil.