The Hangover part III is...different. Different in the sense that the Hangover part doesn't make sense other than being a continuation of what happened the last time around. Well, it didn't involve in any sort of blackout which result in memory lapse in them. So this time around, they remember every single detail of their wacky adventure.
So the 3 decided to devise a plan so that they can get Doug back and get on with their lives. Their initial plan was to drug Chow and bring him to Marshall. Will they succeed in getting Chow and get him to Marshall? Find out by watching the movie!