Renaissance Italy 1465: After six decades of domination by Florence, agitators in Pisa are taking action. They remember the past when Pisa was an independent State and they are impatient to regain that freedom. Rumors of an impending insurrection reach officials in Florence who dispatch Nico Argenti and his team to find and stop the troublemakers before they resort to violence.

Nico and his colleagues conceal their identities as Florentine Security Commissioners to gain the confidence of Pisan loyalists. The ploy lets them unearth clues, some valuable and some red herrings, that point to the rebel leader, but it also sets Nico as a target.

The hunt turns urgent when the rebels show their resolve by abducting the provincial governor. Nico’s  team intensify their efforts to discover the source of the rebels’ weapons which, surprisingly, leads them back to Florence. In Florence’s highest court, Nico uses his legal skills to bring the traitorous arms dealer to justice.