Rainbow Six: Vegas begins in Mexico during an operation to capture Irena Morales, a Mexican terrorist who is sneaking illegal immigrants across the border. The attempt to snatch Morales fails, but the team is able to unveil a plot aimed at Las Vegas.
Vegas places a heavy emphasis on using cover using an active cover system. You only take cover when holding the (L1) button; otherwise you are left in the open. This has its advantages since it makes it easier to slide from cover to cover, though it is also easy to forget and let go of the trigger, exposing yourself. And believe me... you don't want to expose yourself. The system works, though there are a few instances where you can't use cover in an area you realistically should be able to, or you take cover where you don't intend to.
While in cover, you can pop out and take a few shots or blind fire around corners. The first gives you better accuracy, though it leaves you open for a few hits; the second keeps you safe, but you're not likely to hit anyone. Firing blind is better used as an intimidation tactic in multiplayer games. In single-player it has its uses, mostly when someone is on top of your position, though the A.I. typically doesn't react.
With the exception of a few missions, you are always joined by two teammates. By itself, the A.I. does a great job of staying out of trouble. Pathfinding, which is typically a problem in any game, isn't an issue. Both are also good about covering your back and staying alive.
Level design is open and allows for varying tactics. How you go about taking down cells of enemies is up to you and there is no "wrong" way to do anything. Most areas are built with multiple entry points, so you can send your team through one door while you charge in from another or have everyone rappel down the side of the wall and crash through the window. Pacing is quicker than most tactical shooters. Waiting around isn't an option, forcing you to constantly be on the move and always thinking.
Up to four players can tackle the Story mode cooperatively. In addition, a full slate of competitive modes is also available for up to 16 players. All of the modes should be familiar to online players, and the few new modes are simply new takes on old favorites. Online play is generally smoother than on the 360, though it does have its problems. Voice chat is available, though not everyone can use it since few people own headsets. In the event you manage to find a chatty player, the voice quality is sketchy - sometimes it is clear while at others, it is muffled or scratchy. Finding games presents a few problems as well; you can search for nearly every match parameter you can think of except server size, so you never know what you'll get there.