Hitman: Absolution was one of the key games of this year's E3. The wall outside Square Enix's presentation room was adorned with "Game of the Show" nominations, but these trophies merely acted as physical confirmation of what was already patently obvious: Agent 47 has become the most popular slaphead since Michael Stipe, and next year's reboot is going to be a very big deal indeed - for IO Interactive, for Square Enix, and for the gamers everywhere. Especially the bald ones.

While the Hitman series has been around for a decade now, it's fair to say that past entries have arrived without the fanfare that currently surrounds Absolution. It's not hard to see why the current game has such electric buzz, however: it looks exceptionally slick, with a moody art style and a load of violent new tricks for our folically-challenged felon. In short, it has all the flash and swagger required to be a major event in the action game calendar - and yet long-time fans may be less perturbed by Agent 47's homicidal antics than by his forthcoming mutation.

At the start of the E3 demo, our domed assassin finds himself surrounded by the police in an ancient, dusty library. It's an immediate change from the Hitman setup we've all come to expect: 47 isn't on a job here; he's a hunted animal fleeing for his liberty, and quite possibly for his life too. Other shifts are immediately apparent: the gloomy aesthetic and driving rain outside the building herald a serious shift in tone, while the cops soon reveal themselves to be far more talkative than the silent NPCs of past Hitman games. They seem to be constantly calling out instructions, observations and retorts to each other - particularly in the direction of a squeaky-voiced new recruit - creating an ongoing backdrop to your silent machinations.

While 47 himself has gained a few athletic skills, shedding the slightly ponderous movements of old, some of his new tricks are actually revisions of his older abilities. He's still capable of sneaking up behind people, but now there's no need to perform that slightly silly skulking manoeuvre - you know, the one that seemed to scream "I'M SNEAKING UP BEHIND YOU!" Instead, any slow movement behind a target appears to be automatically silenced, and when you finally reach your victim-to-be, you'll be able to choke them, stab them, or clonk them over the head with what appears to be a vast variety on animations, depending on the object or weapon you currently have to hand. At one moment in the presentation, the demonstrator strangled a cop to death with a power cord.

The cover-to-cover system is now looking a lot slicker (and a lot more necessary), and at one point 47 shimmies along the lip of a walkway, tugging a passing cop over the edge in Assassin's Creed / Uncharted style. However, the biggest influence on display here is actually Batman: Arkham Asylum. By triggering 47's 'Instinct' you'll jump to his point of view, with all nearby NPCs highlighted via sparkling outlines. Even more helpfully, Instinct mode gives you a short projection of where people are about to move. In the demo, 47 used this boon to supplement his established "fusebox sabotage" routine: knock out the power, watch to see where the guards are heading, then creep away with impunity.

The latter half of the E3 demo proves more controversial in terms of the contrast with the established Hitman formula. After slinking around the entire library without being spotted, 47 is confronted by a massive crowd of police officers. At this point he steps out into full view and takes a hostage - the wet-behind-the-ears recruit mentioned earlier - nabbing the victim's gun in the process. The cops yell and spread out in an attempt to cover 47 from every angle, angry red indicators flashing all over the screen. Our man retreats, then floors his hostage and makes a dash for the outside world, trading bullets as he goes. Outside, he finds himself in the spotlight of a police helicopter. As the chopper (or perhaps someone aboard it) opens fire he dashes for cover through a rooftop pigeon coop, gifting the demo its most impressive sequence: a chaotic mix of bullets, broken glass, splintering cover and dynamic lighting.

Shortly after this our suited snuff-merchant manages to subdue a stray cop, stealing his uniform and slowing the pace of the action in the process. Disguised, Agent 47 gains access to a nearby apartment that just happens to be home to a set of stoned (and rather paranoid) weed dealers. This sequence offers the first signs that Absolution may still contain some of the dark humour that characterised its predecessors, mining plenty of comedy from the situation and providing some unusual impromptu weapons. It appears that there's some form of in-game challenge/achievement system, so I'll leave it to you to work out what the "Bong Hits" tracker might relate to.

The last section of the demo heavily recalled the last act of Luc Besson's Leon (or The Professional, if you're a US reader). In a tense climax, the still-disguised 47 attempted to descend through a busy apartment building packed with patrolmen and SWAT officers. The Instinct mechanic raised its head again here, allowing 47 to perform an action that will help him to blend in with his surroundings - in this case, he raised the collar on his uniform. There's a nice tense slow-down effect in place when someone starts to look at you directly, your disguise gauge filling as you fall under detailed scrutiny. It also seems that you can use specific objects to help you hide in plain sight, loitering by a box of donuts left for the amassed troops, for example.

Even here it's not entirely clear how safe you'll be. While at the refreshments table one cop started showing a keen interest in Agent 47, mistaking him for an old colleague. The do-gooder started harping on at 47, who responded only with steely silence and the occasional non-verbal response. For a while discovery seemed imminent, but then our new friend abandoned his attempts at conversation. Is it possible to be rumbled here? It's not clear, but the moment certainly shows how the new chatty NPCs can be used to amplify tension.

The whole experience looks thoroughly impressive, and there's no doubt that Hitman Absolution will cause a big splash if the full game is as detailed and as carefully-produced as this demo. However, I also think that veteran fans of the series will be up in arms about some of the departures on display. While we've got to be careful about assuming too much on the basis of one presentation, it does seem that Absolution has shed much of the open nature and forward planning that distinguished the series in the past. There's no map, so it seems you're encouraged to be reactive rather than proactive, and in contrast to Agent 47's established MO, it didn't seem as if there was much punishment for killing innocents.

We're used to playing Hitman like professionals - going unnoticed, and making our hits look like accidents - but at times the Absolution demo felt worryingly close to The Bourne Identity. This was especially true during the "high octane" segment, leading up to the confrontation with the chopper. It seems hard to believe that you'll be able to skip such an orchestrated set-piece, and yet it's this kind of thing that will put the collective nose of fans out of joint. The name of the game is "Hitman" after all, not "Runaway Cop-Killer".

Still, IO Interactive has promised that it has stayed loyal to the spirit of the series, that Silent Assassin ratings will return and, most importantly, that you'll be free to find your own way through each level. In all fairness, this last element is the kind of thing that's very hard to show off in a 15-minute E3 demo; on the other hand, you can't blame people for having concerns about the apparent changes - or indeed for lamenting the absence of Jesper Kyd, whose excellent scores contributed greatly to the Agent 47's past outings.

Regardless, few would question the technical quality of the game we saw last week, and IO has certainly succeeded in grabbing everyone's attention. One thing's for sure: Hitman has changed, and from here there's no turning back.

Hitman Absolution is due for release on Xbox 360, PS3 and PC in 2012.