A dissident Russian journalist uncovers a shadowy mercenary army in Syria, sparking a dangerous investigation that spans three continents.

Katya is reporting in Syria when she stumbles upon the operations of Wagner, a mercenary company with a brutal reputation led by Yevgeny Prigozhin. She teams up with Denis, an exiled police detective, to investigate Prigozhin's expanding network. Together they unravel Wagner's reach through Ukraine, the Central African Republic and beyond. As Prigozhin's power grows, so does the personal cost of pursuing him. Still, Katya and Denis push deeper, determined to expose evidence of war crimes and go public with their findings. Hell's Army follows them as they race against a machine that is growing faster than anyone can keep up with.

Content guidance: contains graphic footage of violence and torture.