Every year, 310 killings in France go unsolved, leaving the victims' crushed families in a state of endless grief. The French judicial system is implacable there's no money to continue investigating cases that lead nowhere. Hunting down murderers to help bereaved families get justice is more than just a job, it's a duty for Thomas Bareski, a retired, hotshot police detective. A wandering, footloose, nature-loving soul who lives out of his van, Thomas Bareski isn't just a one-of-kind man, he's also an extraordinary police officer who's ready to upend his way of life to fulfill his mission.

穷极潦倒的克莉丝汀（凯瑟琳·弗洛 饰），寂寞地穿梭在巴黎市街，日复一日地寻找食物银行的补给品维生。在一个天寒地冻的冬日，八岁小男孩苏力（玛哈玛杜雅法 饰）站在她的栖息之处哭泣。询问后，克莉丝汀发现苏力跟母亲走散了，而两人的相似处境，让她们一同步上充满了爱与希望的寻亲之旅，共同勇闯巴黎的地下世界，试图寻找苏力的母亲。

二十岁的大卫是个活在当下的空想家，没有固定工作以打散工糊口。他邂逅了刚移居巴黎的莲娜，很快便堕入爱河。但没多久之后，他平静的生活却因姐姐在一次袭击中猝然身死而突然终断。在震惊和伤痛之余，大卫还发现自己要独自照顾七岁的侄女阿曼达。