This introductory instance is known as Tokyo Flashback, and not only does it serve to introduce players to the mechanics of combat within The Secret World, but it also sets up the game's conspiracy-laden storyline by introducing players to four key characters of The Secret World's universe. Most players will be familiar with these characters from the title'sprevious trailers, including the one from Gamescom 2011.
The demo of Tokyo Flashback follows a shotgun-toting heroine as she tags along with the NPCs against a horde of infected humans known as the Filth. The demo also imparts some new knowledge of gameplay mechanics. For instance, mobility is very important, and few -- if any -- abilities will root the character in place, allowing players to move freely at all times. It's also revealed that combat (or shotgun combat, at any rate) uses a combo-point-esque mechanic wherein certain attacks build resources on a target, and other "finisher" attacks expend those resources.
For the full trailer, head on past the cut, and check out the write-up of the Comic Con panel over at The Hydra Initiative. And don't forget, players interested in beta-testing The Secret World can sign up for The Secret War on the game's official site.