View it as a spin off and it's a rollicking treasure seeking adventure.
Ok lets have it out front right away, this particular writer loved the first film (Curse of the Black Pearl), was disappointed with the second (Dead Man's Chest) and positively found the third (At World's End) to be an incomprehensible bore. Part 4: On Stranger Tides is a shift in another direction, where a group of piratical characters, some we know well, others new to the fold, embark on missions to find the fabled Fountain of Youth. So think "Indiana Jones", "National Treasures" like adventures (hell even "It's a Mad... read the rest.
Not a bad movie. Part 4 has Jack Sparrow on a quest to find the fountain of youth. A lot of the important cast that helped make the movie are not in this movie.