We haven't gone far off AC 2's beaten path quite yet. Where the sequel had continued to push its Dan Brownish narrative toward its final denouement, Brotherhood extends it a tad longer. Or it extends Ezio's participation in the plot, anyway. And so we're back in Italy, just where we left off in the last game.
AC: B's main conceit is in establishing the Brotherhood, which is the most obvious change in the series. Now a Master Assassin, Ezio is in the throes of reorganising the entire order to fight against the Templars in Rome, and new members are recruited by completing missions scattered around the city.
Past instalments had you buying off citizens to help you with your task - you'll remember the happy prostitutes who you'd throw a shilling at to get them to shimmy around you, shielding you from passing guards. And, generally speaking, the Brotherhood is what would happen if this little bean of an idea grew into a fully-formed management system.
A few trailers have already shown what they're capable of, functioning as a kind of special attack used against nearby enemies: select a guard, whistle, and any free assassin will drop from as rooftop to take him out. However you can also level them up, customising their appearance and weapon loadout, by spending skill points earned by doing things such as sending them across Europe to fulfil their own assassination missions.
Whether it's particularly necessary to have an entire brotherhood backing you is a question not fully answered in the demo. Back in the days of AC and AC 2 enemy AI had the tendency to queue up to fight you. AC: B is admittedly cleverer with its AI, and so the pacing of combat has an entirely different rhythm. Where Assassin's Creed 2 emphasised counter-attacks, Brotherhood's mantra is "strike first, strike fast". You'll often have two enemies attacking you simultaneously, and likewise you can come at them with a sword in one hand and a hidden gun under your sleeve to deal with stragglers. Ezio is built to handle himself. Even with a sword alone he uses a basic kick-and-stab strategy: kick the nearest opponent so he staggers backwards, giving you enough time to stab the second nearest, and so on in a chain.