Hunting ISIS

Unpaid and unsanctioned by their own government, a handful of American volunteers leave their homes and loved ones to join the fight against ISIS in Iraq and Syria.

PJ transfers to an offensive unit in Syria where he's assigned to liberate the ISIS-held town of Al-Shaddadi; he forms a bond with Levi, a young jokester from Colorado; in Iraq, medics Pete and Derek get dangerously close to the front lines.

In Syria, PJ's unit attacks the city of Al-Shaddadi but avoids heavy combat; a frustrated PJ heads home; in Tennessee, Jeremiah is desperate to return to war; new faces join Pete's medical team in preparation for the impending siege of Mosul in Iraq.

The long-anticipated siege of Mosul finally begins on the city's eastern limits; ISIS intensifies their tactics; in the U.S., PJ and Levi's family struggle to reckon with Levi's death; ISIS goes on the defensive in the Middle East.

PJ returns to Syria, inspired by Levi's sacrifice; in Iraq, ISIS is losing ground in Mosul but stages a diversionary attack in the city of Kirkuk; Pete reaches a breaking point as casualties stack up in Mosul; there's still a long road ahead.

Pete returns to Iraq with his girlfriend, Alex; in Syria, a snafu leaves PJ weighing his options; signs of life are reappearing in areas freed from terrorist rule; the volunteers take stock of what they've accomplished and what lies ahead.