Someone stole his master lightning bolt and unless it is returned to him, then a war among the gods will erupt.
Unbeknownst to Percy Jackson, a troubled teen with dyslexia and ADHD, this is a big problem for him, because everyone on Mount Olympus thinks he stole it. Percy is then catapulted into an adventure where he discovers he's the son of Poseidon and sets out to find Zeus's missing lightning bolt.
The Lightning Thief is based on the first young adult (YA) story of Percy Jackson and the Olympians by Rick Riordan. The premise of the series is that the gods of Greek mythology are still with us, and often get the urge to "hook up" with mortals every now and then. Unfortunately, these unions never last, because Zeus issued a restraining order against the gods, forbidding them from having contact with their demi-god offspring.
http://en.wikipedia.org/wiki/Percy_Jackson_&_the_Olympians
While the plot was a formulaic quest and the real culprit was rather obvious, I found the movie to be fast-paced, which was supported by several well-known adult actors. There were however, moments in the movie where I felt Percy and his companions should have handled the encounters better. Especially when one of them, Anabeth, is the daughter of Athena, goddess of wisdom and warfare.
Despite such weak moments, this was an enjoyable movie worth taking the family to see on the big screen. Children already reading YA books will probably get the most out this movie and may encourage them to read the series.
I give The Lightning Thief 3-stars. Since the adult actors were chosen for their "sequel capability," we can expect to see more of Percy Jackson's modern mythological adventures.