On a lonely road on the borders of Wales, a man has crashed his car and died. It seems like a simple accident to everyone except the man's grieving daughter, Angie. She's convinced he was murdered, since -- being a victim of red-green color blindness -- he did not drive. Suspended from his duties, Sergeant Harry Kyle agrees, as a favor to Angie's husband, to examine the facts and put her suspicions to rest. But the more he probes, the more suspicious he becomes -- until someone hits him over the head, and Harry Kyle sees red.