That, and an excuse to oogle the very young, luscious Leelee Sobieski in just her underwear*!!* 
Most every ‘mystery’ about the events of the film are explained to Tom Cruise by Sidney Pollack’s character at the end. He is not an ‘unreliable narrator’ nor part of a ‘vast conspiracy’, everything he says make sense and is true. The film is more about the characters’ emotions and reactions to the seemingly weird events of that night rather than the events themselves…