Director Penny Lane’s decision to become a “good Samaritan” by giving one of her kidneys to a stranger turns into a funny and moving personal quest to understand the nature of altruism. “Confessions of a Good Samaritan” is a provocative inquiry into the science, history, and ethics of organ transplantation, asking an ancient question in a whole new way: Who is your neighbor, and what do you owe them?

• Documentary