Heather Graham and Justin Bartha have signed on to star in Todd Phillips’ comedy “The Hangover,” which heads into principal photography this week, according to the Hollywood Reporter.

The film centers on three best friends who literally lose their best friend during his wild bachelor party in Las Vegas. Together, they have to figure out what went wrong the night before.

Bradley Cooper, Zach Galifianakis and Ed Helms are already on board. Bartha plays the lost groom, while Graham stars as a Las Vegas local who encounters the friends and may be able to help them out in one way or the other.

Graham was last seen in “Miss Conception.” She recently wrapped filming for Duncan Ward’s “Boogie Woogie.”

Bartha is known best for playing Riley alongside Nicholas Cage in the “National Treasure” films. He’ll also appear in “New York, I Love You.”

Phillips is directing a script by Jon Lucas and Scott Moore, who also wrote Christian Charles’ “Full of It” and Mark Waters’ upcoming romantic comedy “The Ghosts of Girlfriends Past.”