A boy dies in a car crash just after having sex for the first time, leaving his girlfriend scared and alone. Sounds like a recipe for a soapy Lifetime movie. Which The Greatest could well have been without a riveting cast that plays it for real. Carey Mulligan, an Oscar nominee for An Education, is wonderfully appealing as Rose, the girl who rings the doorbell of the dead boy’s parents, Allen Brewer (Pierce Brosnan) and his wife, Grace (Susan Sarandon), and announces that she’s three months pregnant. They take her in, Grace resentfully and Allen with a sense of hope. In flashbacks, we see the tentative courtship of Rose and the boy (the excellent Aaron Johnson). But the bruised heart of the movie is uncovered as Rose tries to build a picture of a boy she barely knew from the memories of his family, including his younger brother (Johnny Simmons). First-time director-writer Shana Feste, covering a trail indelibly blazed by Ordinary People, sometimes lets her foray into the spiky corners of grief spill into melodrama. The actors never do. Sarandon nails every nuance as the alienated mom. And Brosnan, on a roll with this film and The Ghost Writer, vividly etches the emotional fissures in a man coming apart. The Greatest takes a piece out of you.