A partially handicapped man named Karl is released from a mental hospital, about 20 years after murdering his mother and another person. Karl is often questioned if he will ever kill again, and he shrugs in response saying there is no reason to. Now out of the mental institution, Karl settles in his old, small hometown, occupying himself by fixing motors. After meeting a young boy named Frank, who befriends him, Karl is invited to stay at Frank's house with his mother Linda, who views Karl as a strange but kind and generous man. However, Linda's abusive boyfriend, Doyle, sees things differently in the way rules ought to be run- normally insulting Linda's homosexual friend Vaughan as well as Karl's disabilities, and having wild parties with his friends. As Karl's relationship with Frank grows, he is watchful of Doyle's cruel actions. 弹簧刀。《弹簧刀》弱智捍卫正义的方式。The Insider（弹簧刀）。He is a boy。给我一把正义的弹簧刀。自编自导自演确实非常厉害。问问题。无题。Just simple i like that feeling。弹簧刀影评：比利大叔的个人SHOW。 天生智能障碍的卡尔（比利•鲍伯•松顿 Billy Bob Thornton 饰）生于一个不幸的家庭：迷信宗教的父母总把他当作上天对他们的惩罚，因而十分厌恶他，老是虐打他。自小生活在阴影中的卡尔，8岁的某天撞见了母亲和一名拉皮条的人偷情，压抑的情绪瞬间爆发，他用弹簧刀将两人都刺死了。自此以后的25年岁月里，卡尔都在精神病院里度过。 出院那天，无家可归的卡尔被精神病院的管理员收留了一个晚上，这是他第一次感到人间的温暖。出院后，人们都想躲瘟神般躲着卡尔，直至他遇上了好友弗兰克（卢卡斯•布莱克 Lucas Black 饰）。弗兰克将他当成自己最好的朋友，卡尔在生活里看到了阳光。然而最近，弗兰克一家被其母亲的酒鬼男友搞得鸡犬不宁。看到朋友受罪，忍无可忍的卡尔，决定挺身而出。
