黑夜，天神宙斯召见海神波塞冬，称其子偷了闪电火，要挟他若不尽快找回，必将开战。现实中，波塞冬与人妻萨利之子波西杰克逊（罗根•勒曼 Logan Lerman 饰）是个大学生，17岁的他可以在水下呆7分钟，但对老师关于莎翁的提问不感兴趣。参观博物馆时，他遇到了摇着轮椅的人马老师（皮尔斯•布鲁斯南 Pierce Brosnan 饰）。而文学老师却变身成了复仇女神，向他逼问闪电火的下落。幸好人马教授和羊男朋友及时赶到，化险为夷。他们带波西来到营地，训练波西，他们找来了一个女战士安娜贝斯（亚历山德拉•达达里奥 Alexandra Daddario饰）与之比武。落败后，触水的波西被激活了潜能，成为奋勇无敌的战士，并开始踏上了追寻闪电火的英雄之旅。面对蛇女美杜莎等神怪的攻击，冥王冥后珀尔赛弗涅的刁难，他的自我救赎只剩下10天……When his lightning bolt is stolen, Zeus accuses Poseidon's son Percy Jackson and gives Poseidon's son fourteen days to return it, otherwise he will initiate a war amongst the gods. Meanwhile the teenager, Percy, who is dyslexic and has ADHD is visiting The Museum of Metropolitan of Art and is attacked by a Fury disguised in his teacher. His physically handicapped best friend Grover reveals that Percy is a demigod and that he is his protector and his teacher Mr Brunner gives him a pen telling him that it is a powerful weapon. They go to Percy's house and together with his mother Sally they drive to the Camp Half-Blood. However Sally is attacked by a Minotaur and vanishes before Percy can help her. In the camp, Percy befriends the gorgeous Annabeth; when they are attacked by Hades who wants the lighting bolt for himself, Percy discovers that his mother is in the Underworld with Hades. Percy decides to travel on a dangerous quest to retrieve the lightning bolt and save his mother. Grover and Annabeth join him and Luke gives a powerful shield of his own to protect Percy. Will they be able to succeed?