After the events of Just Cause 3, Rico Rodriguez is approached by a Sol�s native, Mira Morales, who convinces him to come to Sol�s to uncover the truth about Project Illapa, a project aimed at creating weather cores able to control the weather and generate storms, and one which Rico’s father, Miguel Rodriguez, had a part in creating. The project is run by the incumbent Sol�s leader, Oscar Espinosa, who maintains tight control over the people of Solis.
After a failed attempt at deposing Espinosa, and a run-in with his private army, the Black Hand, led by Gabriela Morales, Rico forms an army of his own with Mira, named the ‘Army of Chaos’, aimed at taking down Project Illapa and ending Espinosa’s regime. Along the way, he meets up with Luis Sargento, an eager commander of the Army of Chaos, Izzy, a hacker, Garland King, a filmmaker obsessed with filming stunts in Sol�s, and Javi Huerta, an archeologist wishing to uncover the history behind Sol�s and the Espinosa legacy. As Rico sets out to destroy the four prototype weather cores being tested in Sol�s, he also meets up with Lanza Morales, Mira’s uncle and a scientist who worked on Project Illapa, C�sar, a former pilot turned conspiracy theorist, and Tom Sheldon, Rico’s old handler at the Agency.