In primitive times, the struggle for life was difficult and dangerous, with high attrition from illness, tribal conflict and environmental challenge. Essential to survival was close human bonding and cooperation. Following flight from their decimated village, Orin and Ivor are inseparable in their bid to find a new life. A chance encounter with strangers engulfs them in a new kind of threat that neither could have anticipated, but one that will test their mutual loyalty to its limits.