Link: An Experiment In Terror (1986)

When Man was given mastery over the beasts, someone forgot to tell...

Elisabeth Shue stars as Jane, a student who has recently gotten a job as a research assistant with Dr. Steven Phillip, who is conducting experiments with chimpanzees. Instructed to travel out to Dr. Phillip's house in the country, Jane is greeted there by Link, an aging chimp in a butler's uniform. There, she observes Dr. Phillip perform a few experiments and does some housework for him. However, one day Dr. Phillip leaves the house and never returns. leaving Jane to deal with some strange men who want Link and three increasingly hostile chimpanzees.