The film is a fine slice of time, revolving around the exact moment the titular peaceful man, Harper, realizes he is capable of monstrous things to save himself; and his transformation into a different man entirely.
A peaceful man, Harper is beaten within an inch of his life by an unnamed attacker. With his knee shattered, his arm broken, and an angle grinder bearing down, Harper reacts instinctively; stabbing his attacker through the eye with a screwdriver. As the two men fall to the ground, Harper reflects on his situation, and comes to the gruesome epiphany that violence is intrinsic to all mankind.