Reaching the island, Will suspects Sparrow may betray him and knocks him out. He rescues Elizabeth, and they escape to the Interceptor. Jack barters with Barbossa—in exchange for revealing Bootstrap's real child and being given the Black Pearl. Jack's negotiations come to naught, however, when the Pearl pursues the Interceptor, sinking her and taking the crew captive. Will reveals that he is Bootstrap Bill's true offspring and demands that Elizabeth and the crew be freed. Otherwise, he threatens to shoot himself and fall overboard, lost forever. Barbossa agrees but craftily applies another loophole and maroons Elizabeth and Jack on a deserted island (the same island Jack was on ten years before) and throws Jack's crew into the brig. Will is taken back to Isla de Muerta for the ritual.
Elizabeth burns an abandoned cache of rum to create a signal fire that is spotted by Norrington. She convinces Norrington to rescue Will by accepting his earlier marriage proposal. Arriving at the island, Norrington sets an ambush outside the cave while Jack goes inside and persuades Barbossa to form an alliance. He tells him to delay breaking the curse until after they have taken the Dauntless and killed the crew. Jack then sneaks a coin from the chest, rendering himself immortal. But whatever Jack's actual intent is, his plan goes awry when Barbossa orders his crew to infiltrate the Dauntless from underwater. Jack's true allegiance is revealed when he attacks and then shoots Barbossa. Jack tosses his bloodied coin to Will, who returns the last two medallions to the chest, breaking the curse. No longer immortal, the fatally wounded Barbossa falls dead. Realizing they are no longer cursed, the now-mortal pirates surrender to the navy. Back in Port Royal, Jack is about to be executed. Believing Jack deserves to live, Will rescues him. Both are quickly captured, but Elizabeth lends her support and declares her love for Will. Norrington releases her from their engagement, and Will is pardoned. Meanwhile, Jack escapes by falling into the bay. His crew, who escaped with the Black Pearl, rescues him. Norrington is impressed enough to allow him one day's head start before giving pursuit.
source:Wikipedia
