The Brute (movie, 1977)

Glamour model Diane Shepherd is routinely being beaten by her husband Tim, who accuses her of infidelity. When she can't take it anymore, she finds shelter with photographer Mark and his girlfriend Carrie. They introduce Diane to Millie, who is in a similar situation. Meanwhile, Tim informs Diane that if she doesn't come back to him, he will see to it that he gains custody of their son, Timmy.