Billy (Michael Douglas), Paddy (Robert De Niro), Archie (Morgan Freeman) and Sam (Kevin Kline) have been best friends since childhood. So when Billy, the group's sworn bachelor, finally proposes to his thirty-something (of course) girlfriend, the four head to Las Vegas with a plan to stop acting their age and relive their glory days. However, upon arriving, the four quickly realise that the decades have transformed Sin City and tested their friendship in ways they never imagined. The Rat Pack may have once played the Sands and Cirque du Soleil may now rule the Strip, but it's these four who are taking over Vegas.