The following version of this book was used to create the guide: Ausubel, Ramona. The Last Animal. Riverhead Books, 2023.

Following the death of her husband, Sal, a biologist and researcher named Jane Drake travels to Siberia with her two daughters, Eve and Vera, in order to assist her professor at a dig site for mammoth bones. Although in some respects the two young girls are intrigued by the Siberian landscape, they have long resented their parents' habit of carting them around the world in pursuit of their scientific work, and Eve, the older of the two, fears she will never find love or live a normal teenager's life. Upon arriving in Siberia, the operator of the dig site, Dmitri, explains to Eve and Vera that there are efforts underway to reintroduce the mammoth to the tundra and steppe, a development that would reduce carbon emissions by helping keep heat trapped in the ground under pack snow. While the adults conduct research and sample analysis, Eve and Vera wander out across the steppe and come across the preserved carcass of a baby mammoth, which they excitedly bring back to camp. The men at camp celebrate and claim the discovery as their own, much to the outrage of the two girls.

After the work in Siberia concludes, Jane returns to Berkeley with her daughters and begins analyzing the mammoth carcass in her professor's lab, where, much to her dismay, the most valuable work on the body's study is given to a hapless post-doc named Todd. Jane has to attend a scientific gala and spends the night furious at the dismissals of her male coevals before having a chance encounter with a wealthy benefactress named Helen MacDaniel, who invites Jane to conduct her mammoth breeding research on the grounds of her castle in Italy. Jane impulsively steals mammoth embryos from her professor's lab and brings them to Helen's castle near Milan, where Helen's husband, George, inseminates an adult female elephant with the mammoth embryos. Eve and Vera are somewhat disturbed by Helen's lifestyle, and they enjoy settling into a relatively normal routine when Jane returns from Italy. However, upon learning that the elephant has, against all odds, become pregnant, Jane decides to take a position conducting research in Iceland, disrupting her daughters' lives once again.

While in Iceland, Eve falls in love with a local boy named Lars, and the two begin meeting regularly to have sex with one another. In the meantime, Jane has some samples from a prehistoric iceman shipped to her from Italy because she wants to continue the research that her husband, Sal, was in the midst of before he died. One night, Vera tattles on Eve to Jane, who drives to Lars' house, finds Eve and Lars in bed together, and demands that Eve return home with her, announcing that she is no longer allowed to spend time alone with Lars. Furious, Eve rashly decides to attempt to impregnate herself with samples from the iceman, which infuriates Jane, who feels that Eve has intentionally sabotaged the last of her father's work. This infighting becomes irrelevant, however, when Jane learns from Helen that the baby mammoth has been born; the three women rush to Italy, find the castle abandoned because George has been rushed to the hospital with an injury, and spend the next several days attempting to nurse the baby mammoth with little idea what they are doing.

When Helen returns from the hospital, she insists that the girls recover, an effort that goes well enough until Vera discovers a positive pregnancy test in Eve's belongings and confronts her about the possibilities. Although Lars dismisses Eve when she calls him for help, and Eve is disturbed by the thought that the pregnancy might be by a prehistoric iceman, the sisters decide to attend dinner with an exuberant Helen, who begins laughing about the fact that her husband George was trampled by the mother elephant. When George returns to the castle, Eve and Vera spend time with him to try to gather information, and Vera notes that George has been collecting samples from the baby mammoth and secretly keeping them in his chambers. After speaking with George, the girls take a boat ride on the lake at Helen's prompting, and are concerned when the boat begins to sink while they are out on the lake; they assume that Helen is trying to kill them. When they return to their mother, they urge Jane to leave Italy and to let them visit the location where their father died, but Jane is hesitant, not willing to abandon the mammoth calf.

The next day, Helen decides to organize a ball in celebration of George's birthday, and the girls decide to get dressed up and bake a cake to bring to the reception. Helen helps them pick out dresses and reassures them that she is not their enemy, even gifting Eve an expensive diamond necklace. During the party, Eve confesses to Jane that she is pregnant, leading the two women to reconcile, while Vera confronts Helen and asks her whether their lives are in danger, prompting Helen to inform Vera that they are safe but that George wants to sell the mammoth to an exotic animal collector. Vera urges Eve and Jane to pack all their belongings into a van on the castle grounds and flee the area along with the mammoth. Jane brings the girls to the site of their father's accident, then stops the van by a mountain meadow and allows the mammoth to wander around and graze before it walks into the woods and they watch it go.