Tom Raines and his friends are eager to return to the Pentagonal Spire to continue their training for the elite Intrasolar Forces. They're in Upper Company now, vying for spots in CamCo, but soon discover troubling changes: strict new regulations, suspicious agents in positions of power, and the revelation that the Spire is under new military control. The trainees are now cadets.

What begins as an irritating adjustment soon reveals a dangerous shift in reality. Those now in control are aligned with the corporate sponsors who have ruthless agendas. And when the military academy begins welcoming new cadets with questionable neural processors, the first step in a plan with horrifying worldwide ramifications, Tom is desperate to stop it, even if that means keeping secrets from his allies.

Then a mysterious figure, the other ghost in the machine, begins a fight against the corporations, but with methods even Tom finds shocking. And when the enemy comes for Tom, how much can Tom endure in the battle to save himself? He must decide if he can still fight when the odds of success seem to be sliding from his grip.

In this exhilarating, explosive, and heart-rending conclusion to the Insignia trilogy, Catalyst brings Tom and his intelligent, passionate, and brave young friends stunning tests and dangerous confrontations, and through to an impossible future they could never have predicted.