查理(汤姆·克鲁斯 Tom Cruise 饰)父亲去世,留下了300万美元的遗产。然而令他意外的是,遗产全部给了一个他不认识的哥哥雷蒙(达斯汀·霍夫曼 Dustin Hoffman 饰)。雷蒙的名字查理从没听过,这个事件让他气愤不已。他决定前去寻找哥哥。谁知雷蒙的住处就在一个精神病院里,原来他自幼患有自闭症,母亲去世后就被送到精神病院治疗。查理心中有了算计,他把雷蒙带出精神病院,企图骗他出让遗产。 雷蒙的生活习惯奇异,活在自己的幻想世界里,有很多离奇古怪的行为。并且,查理在共处中发现了雷蒙惊人的记忆能力,他试着利用哥哥过目不忘的本领去赌场上试一下身手,赢得了一大笔奖金,使查理足以摆脱穷困生活。而令查理收获更大的是,他还获得了慢慢升温的亲情,这种手足情远远胜过了他原先图谋的300万的遗产。Charles Sanford "Charlie" Babbit is a self-centered Los Angeles-based automobile dealer/hustler/bookie who is at war with his own life. Charlie, as a young teenager, used his father's 1949 Buick convertible without permission and as a result, he went to jail for two days on account that his father reported it stolen. It is then that Charlie learns that his estranged father died and left him from his last will and testament a huge bed of roses and the car while the remainder will of $3 Million goes into a trust fund to be distributed to someone. Charlie seemed pretty angry by this and decides to look into this matter. It seems as if that "someone" is Raymond, Charlie's unknown brother, an autistic savant who lives in a world of his own, resides at the Walbrook Institute. Charlie then kidnaps Raymond and decides to take him on a lust for life trip to the west coast as a threat to get the $3 Million inheritance. Raymond's acts and nagging, including repeated talks of "Abbott & Costello", "Four minutes till Wapner" and refusal to fly on an airline except Quantas drives Charlie insane... and out of his selfish world into a cross-country trek of pure love and understanding that these two both have.