An urban spelunking group in San Francisco discovers a secret bunker belonging to the long-vanished 1930s stage magician Blackhall the Incredible at the same time as young, out-of-work magician Ivan receives a mysterious package that points him toward a possible conspiracy involving Blackhall's death in 1934. Both groups dive into the mystery, not yet realizing that it's about the change their lives forever.
Ivan, Harumi, and Niko venture back into Blackhall's bunker, and this time, they stumble on more than they bargained for. As more secrets are revealed about the conspiracy surrounding the magician, the members of Backbone start to realize that this may be their most dangerous exploration yet.