Forty-thousand years in the past, the last family of Neanderthals roams the earth. After a crushingly hard winter, their numbers are low, but Girl, the oldest daughter, is just coming of age. Her family is determined to travel to the annual meeting place and find her a mate. But the unforgiving landscape takes its toll, and Girl is left alone to care for Runt, a foundling of unknown origin. As Girl and Runt face the coming winter storms, Girl realizes she has one final chance to save her people. In the modern day, archaeologist Rosamund Gale works well into her pregnancy, racing to excavate newly found Neanderthal artifacts before her baby comes. Linked across the ages by the shared experience of early motherhood, both stories examine the often taboo corners of women's lives.

While camping with her family on a remote island, five-year-old Anna awakes in the night to the sound of her mother screaming. A rogue black bear is attacking the family's campsite and pouncing on her parents as prey. At her dying mother's faint urging, Anna manages to get her brother into the family's canoe and paddle away. But when the canoe runs aground on the edge of the woods, the sister and brother must battle hunger, the elements, and a wilderness alive with danger.