By Russ Fischer/March 2, 2011 10:30 am EST

The books are bestsellers, but the film did only modest tentpole business in 2010: under $90 domestic. But it did $138m overseas. Not enough to push the profit margin definitively into the black when all expenses and cuts are factored in, but enough that projected long-tail revenue evidently makes a sequel look like a good move.

In this second adventure in Percy Jackson and the Olympians series, Percy is anticipating the end of seventh grade and a summer at Camp Half-Blood with kids who are the offspring of Greek gods and mortals. He dreams that his pal Grover, a satyr, is in danger. After monsters attack in his school gym class, Percy and Tyson, a homeless kid, are picked up by Annabeth, a half-blood friend, and rushed to the camp, which is under attack. The tree that guards the camp is dying, and Chiron, the activity director, has been dismissed. Another dream reveals that Grover, whose peril is increasing, is on the same island as the legendary Golden Fleece, which may be the cure for the troubled camp. With the help of Hermes, Percy and his pals set off to the Sea of Monsters, where they encounter legendary dangers.