The Ugly Little Boy(1977)

Edyth Fellows is a nurse recruited for an research project with a time travel device that can snatch any being from any time and bring it to the present. The first such test brings an Neanderthal child to the project and Fellows is responsible for his care for the interim. As she manages this task, Fellows is increasingly revolted at how the scientists dismiss him as little more than an animal, especially when his real intelligence shows. This growing moral dilemma comes to a head when Fellows realizes what they plan to do with him and she cannot stand by and let it happen.