Los Angeles, 1890. It's the golden age of industrial innovation. For 15-year-old Alroy Doyle, obsessing over the mechanical marvels of this era - like hydraulic horses and soaring airships - has become the only way he can distract himself not just from his father's recent death, but also how the last words he ever spoke to him were in anger.That's why he and his twin sister Zella are proud members of the League of the Daring - a secret society of teenage futurists who study science and technology under the watchful eye of the brilliant Doc Grimes. To the League, all this incredible innovation is building the foundations of a bright new future.But when classmate and fellow League member Pedro Hernandez disappears, Alroy and his sister discover there's a sinister side to their scientific endeavors. With the lawmen of the Los Angeles Police Department unwilling to investigate, Alroy and the League must take it upon themselves to discover what's happened to their missing friend.But what the League of the Daring uncovers is far more sinister than any of them could have imagined - and unless they take immediate action, the bright future Alroy and his friends have been so excited about building could soon be erased from our timeline entirely.