09/12/2012 at 03:30 PM EDT
Melissa Leo has never been what she'd call an animal lover, though dogs and cats have made their way into her life over the years. "It always seemed like they happened upon me," she says. In her new movie, Francine
, however, she plays a woman obsessed with them.
She was able to pull it off because, above all, Leo is an actress, and she relished the experience of "walking inside the soul of another human being" for the independent film about a woman just released from prison.
That namesake human being reveals very little of herself through language – there is hardly any dialogue – but she demonstrates an extreme connection to animals and behaves almost animal-like as she takes jobs at a pet store, horse stables and an animal hospital, all while taking in pets of her own.
"To be an animal myself" was the goal, Leo tells PEOPLE. "For Francine, she doesn't know how to [interact] with people very well and so [interacts] with animals ... In the end, she doesn't really know how to nurture the beasts."
Leo filmed scenes with her son's dog, a yellow Lab named Zeus who died recently at age 15; nuzzled kittens; held a dog as it was anesthetized for a tooth cleaning (rendered in the film as a euthanasia procedure); and gave a horse a bath.
While she ultimately didn't become Francine, she did "work inside of her" long enough that as filming progressed, she became more in tune with her furry costars.
"It was really fun working with the animals," Leo says. "It was very gentle and careful. They're such good actors! They just be