Wikipedia's explaination is better than I can write- so a tip of the hat to them as I cut and paste what they wrote: Lord Beckett gains power over Davy Jones, and with the help of Jones' ship, The Flying Dutchman, he is now executing his plans to extinguish piracy forever. To stand against the East India Trading Co., Will, Elizabeth, Barbossa, and the crew of the Black Pearl set out to rescue Captain Jack Sparrow from Davy Jones' Locker. Sparrow, as one of the Nine Pirate Lords, is needed in order to summon an ancient goddess, with the power to defeat Beckett's forces