Columnist Steve Lopez (Robert Downey Jr.) is at a dead end. The newspaper business is in an uproar, his marriage to a fellow journalist has fallen apart and he can't entirely remember what he loved about his job in the first place. Then, one day, while walking through Los Angeles' Skid Row, he sees the mysterious bedraggled figure Nathaniel Ayers (Jamie Foxx), pouring his soul into a two-stringed violin.
At first, Lopez approaches Ayers as just another story idea in a city of millions. But as he begins to unearth the mystery of how this alternately brilliant and distracted street musician, once a dynamic prodigy headed for fame, wound up living in tunnels and doorways, it sparks an unexpected quest. Imagining he can change Ayers' life, Lopez embarks on a quixotic mission to get him off the streets and back to the world of music.
But even as he fights to save Ayers' life, he begins to see that it is Ayerswith his unsinkable passion, his freedom-loving obstinacy and his valiant attempts at connection and lovewho is profoundly changing Lopez.