Hunting ISIS

The long-anticipated siege of Mosul finally begins on the city's eastern limits. ISIS intensifies their tactics, meaning mounting casualties for the medics and an increasing emotional toll on Pete. In the U.S., PJ and Levi's family struggle to reckon with Levi's death, even as his body remains in Syria. ISIS is on the defensive in the Middle East, but progress comes at a steep price for the volunteers.

PJ returns to Syria, inspired by Levi's sacrifice and intent on reaching ISIS' "capital," Raqqa. In Iraq, ISIS is losing ground in Mosul but stages a diversionary attack in the city of Kirkuk, where Italian volunteer Alex leads his men into battle against them. Meanwhile, Pete reaches a breaking point as casualties stack up in Mosul.

A reinvigorated Pete returns to Iraq with his girlfriend Alex at his side. In Syria, an unexpected snafu leaves PJ weighing his options. Facing inevitable defeat in both countries, ISIS is determined to cause as much damage as possible on its way down. But signs of life are reappearing in areas freed from terrorist rule. In the minds of the volunteers as well, hope begins to creep in as they take stock of what they've accomplished and what lies ahead.