Harka darts between genre conventions: One minute it feels like a thriller, the next a heart-wrenching drama, another a psychological study. When the risky mix-and-match works — and sometimes it doesn’t — the results are emotionally potent. Nathan is fascinated by desperation, the kind that roots itself in the mind and soul. What lengths will a desperate person go to in order to survive? That is the essential, thrilling question coursing through Harka.