Sean McCaffrey, the son of the late firefighter Stephen "Bull" McCaffrey, follows in his father's footsteps as an investigator with the Chicago Fire Department. Haunted by his father's legacy and dealing with personal demons, Sean gets assigned to investigate a series of fatal fires. He's paired with Maggie Rening, an experienced but tough investigator who challenges Sean's methods and inexperience. With tensions mounting between them, they discover a disturbing pattern involving the use of sophisticated fire-starting techniques implicating arson that seems to be linked to an international terror plot.

As their investigation unfolds, the stakes escalate dramatically, pulling Sean into a web of deceit and endangering lives across the city. Sean's determination to prevent further tragedy forces him to confront his fears and embrace his heritage as part of a firefighting family. With the help of veteran firefighter Brian McCaffrey and a reformed arsonist named Ronald Bartel, Sean uncovers layers of conspiracy that reach far beyond simple arson. The investigation not only tests Sean's resolve but also has him racing against the clock to prevent a catastrophe.