Butterfly Kiss (1995)

Deeply mentally unbalanced drifter Eunice roams grim northern Britain committing psychosexual serial murders of both men and women while ostensibly searching for an unknown woman named Judith. She spares the life of lonely but kind-hearted gas station cashier Miriam, who abandons her dismal life to follow her damaged new lover. While attempting to hide the evidence of her multiple crimes, Miriam tries to understand Eunice's bizarre quest.