Todd Phillips says 'The Hangover Part III' is "Alan's story".
The director will once again helm the movie - the third and final instalment of the comedy franchise - and says the plotline will be focused Zach Galifianakis' character.
He told Entertainment Weekly magazine: "He's going through a crisis after the death of his father, [and] the Wolfpack is all he has."
Although he won't give too much away, Todd also says the third film "brings the group together when something from the first movie comes back to haunt them".
Last year, Todd said the highly-anticipated film wouldn't follow the blackout blueprint of the last two movies.
He said: "It's certainly not in the same template that you've seen for these movies. The third would be very much a finale and an ending. The most I could say about it...is that it is not following that template but very much a new idea."
As well as Zach, the movie - which is out next year - will also see Bradley Cooper, Ed Helms, Justin Bartha and Ken Jeong all reprise their roles.