The Hidden Base (Tomorrow's Ancestors, #2)

She wants to escape the past. Is she doomed to repeat it? In the spectacular sequel to Subject Twenty-One, Elise and her friends have unearthed the truth that has been kept from them their whole lives and escaped the Museum of Evolution - but at what cost?

After a perilous escape, Elise and her companions have made it to the safety of the secret fifth base, Uracil, but her family is still in danger. Desperate to secure them passage and a safe place to live, she makes a deal with the leaders of Uracil - she'll become their spy, jeopardising her own freedom in the process.

But first she has to help rescue the next Neanderthal, Subject Twenty-Two.

Twenty-Two has never left the confines of the steel walls that keep her separated from the other exhibits. She has no contact with the outside world and no way of knowing why she has been abandoned. With diminishing deliveries of food and water, she has to start breaking the museum's rules if she wants a second chance at living.

One belongs to the future and the other to the past, but both will need to adapt - or neither will survive.