When news of his brother's murder reached him, aether pilot John Farnley raced back to his old family home.
While he comforts his bereaved sister-in-law, and tries to sort the family business and holdings, he also wonders why his brother, Lord Nicholas Farnley, had ventured into the cramped streets of the East End of London where he had met his violent end. The slums are a deadly place where life was cheap and murderous thugs preyed on the weak and lost.
Now, in the midst of a thick, London fog, something even more monstrous is waiting in the mist-shrouded shadows. Something that has been brought to life by the refugees crowding Bethnal Green and Mile End. Something his brother might have had a hand in creating.
Aided by his friend, the resourceful Miss Sylvia Armley, his own understanding of the aether lines that flow above London, and guided by the erudite advice of Professor Entwistle, John is forced to find his way through the darkest part of London to avenge his brother and stop whatever aether powered monster is lurking there.