NOTE: Review will contain as few spoilers as possible, please continue to exercise caution.
Watching a big event movie that's also a big fantasy/action sequel is always kind of an unusual experience for movie geeks, because it affords "us" the chance to see the mainstream audience "geek out" over something. When something like the first "Pirates" becomes a big deal, "everyone else" starts embracing their inner nerd, keeping track of the franchise mythology in their heads, gasping at the return of characters thought departed (in one way or another) and excitedly chatting with friends about "what'll happen next" once the film reaches it's "to be continued" climax. That the "pop culture phenomenon" of the series owes more to Johnny Depp's whacked-out performance as Capt. Jack Sparrow than it does to the increasingly dense, increasingly fanciful and increasingly creature-laden "The Mummy,' only with water" storyline is eventually not the point: Audiences are packing theaters for an action film about sea monsters, magic treasure chests and scheming British naval traders, and that only bodes well for the genre.
Wisely departing from the lengthy set-up of the previous film, "Dead Man's Chest" presumes the likely audience fore-knowledge of the series' style and mythos and barrells at full sail through a plot that could charitably be called convoluted and more properly described as a dense pack of double-crosses, secret agendas and multiple story-threads. Lingering plot issues from the first film are tied up, while new ones take their place to be continued in the third (final?) installment next year.
Summation of plot would be kind of self-defeating, then, because the "story" keeps going with new twists and rewirings as the film progresses; so to describe "whats going on" would give away the whole chase and with it the whole film. Suffice it to say that the new story largely concerns Davy Jones (Bill Nighy) a centuries-old cursed pirate who roams the sea in a submersible ship called The Flying Dutchman, crewed by damned souls who've chosen servitude to Jones over drowning at sea and have become, like Jones himself, half-man/half-fish monsters. Jones is chasing Jack Sparrow, who apparently owes him such servitude, while Jack is trying (and failing) to use a magic compass to find the fabled "Dead Man's Chest" which he believes contains the key to holding Jones at bay. Meanwhile, back in Port Royale, Will (Orlando Bloom) and Elizabeth (Kiera Knightley) are shanghaied into service by a villianous trader named Beckett, who forces them at penalty of death to chase down Jack and retrieve the magic compass for his own (likely) nefarious ends which seem to have something to do with the enroaching dominance of the seas by British trade companies.
The reason this all works, in spite of itself, is among the reasons that the first film was so surprisingly "not terrible," given the history of films based on theme park attractions: It understands, within the strictures of it's PG13 rating, that the whole fun of making half your characters Pirates means that they DON'T have to obey any kind of moral or even logical code. Thus, double-crosses, sudden changes of heart or moments of outright uncouthness that would be un-do-able in any other film are here quite welcome: They're PIRATES, after all.
To charitable, all of the double-twists and surprises and revelations tend to serve at the behest of creating situations where various characters can clash swords with one another, or be tossed into an impossible escape, or flee an army of monsters, or do battle with a giant squid, or whatever... but thats not the same thing as saying it's not all interesting. On the contrary, jerked around by the invisible hand of fate in the name of a bigger, wilder ride, the series' characters are made to undergo various degrees of situational evolution: Bloom's Will Turner shows ample skill at the art of deception, for example, while Depp takes the perilous risk of plumbing for depth in the studiously-shallow Jack Sparrow. Even newcomer Nighy as the simply incredible Davy Jones goes an unexpected route, delivering a seething, internalized and inquisitive supervillian played with as much subtlety as can probably be managed within a character who has an octopus for head.
But it's Knightley's Elizabeth Swan, until now the series' (literal, at times) moral compass, who's got the biggest "didn't see that coming" personality shift out of the main cast; taking a murky and ULTRA dark character turn in the third act that's garaunteed to throw fans for a "did that just HAPPEN!?" loop just in time for "to be continued."
Two summers ago, the big surprise of the season was that a movie based on a decades-old theme park attraction and that EVERYONE had already decided was going to "suck" turned out to be a great popcorn-muncher diversion. Now, two years later, the big surprise seems to be that that great popcorn-muncher diversion may have had the makings of a grand fantasy/adventure series.
FINAL RATING: 8/10
Memo to Keira Knightley: If in the next few months you see one or more 12 to 16 year-old girls coming toward you on the street at great speed and looking REALLY angry with you... Run. Don't think, just RUN.