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.

Ever wonder what's behind that ""No Trespassing"" sign? Travel into the hidden world of Urban Exploration with the daredevil members of Backbone, the best UrbEx team in San Francisco. When they discover a secret bunker belonging to the long-vanished 1930s stage magician Blackhall the Incredible at the same time a young illusionist receives a mysterious package involving Blackhall's death in 1934, both groups dive into the mystery, not yet realizing it's about the change their lives forever...

Ivan knows he's gotten himself deep into conspiracy land when he discovers that Dmitri is missing and starts seeing a strange, hooded figure following him. Things are about to get even stranger, however, once his investigation leads him right smack into Backbone headquarters. And the urBex team is less than thrilled to meet his acquaintance"¦

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.

Ivan and Backbone recover from the loss of a team member. Knowing now their very lives are at stake, the team must follow new clues even further into the forgotten places of the city. They are finally about to uncover their true enemies, but do they really want to know the truth?

Ivan uses his hypnotism skills on Landell in hopes of finally helping Harumi locate Damon. However, what they learn may not be what they want to hear, especially when it leads them straight into the hideout of the Nonchalants, Backbone's arch-rival urBex team.

With truths revealed, Harumi, Niko, and Damon have to team up with Jackpot and the Nonchalants in order to get Ivan back from S.P.I.. But with so many things going wrong all at once, how can they be sure who to trust, even amongst themselves?

Reunited with Backbone, Ivan must unlock the mysteries of Blackhall's legacy to find the final glowbug and take down S.P.I. once and for all. But will the combined forces of Backbone and the Nonchalants be enough to stop Sir Arthur? Find out in the stunning conclusion to THE LAST BROADCAST!