In 1883, Thaniel Steepleton returns to his tiny flat to find a gold pocketwatch on his pillow. When the watch saves Thaniel's life in a blast that destroys Scotland Yard, he goes in search of its maker, Keita Mori – a kind, lonely Japanese immigrant. Meanwhile, Grace Carrow is sneaking into an Oxford library, desperate to prove the existence of the luminiferous ether before her mother can force her to marry.

As the lives of these three characters become entwined, events spiral out of control until Thaniel is torn between loyalties, futures and opposing geniuses.