We haven't heard much from Garrett in the last nine years, which makes a certain amount of sense considering he's a master of shadows who can go through entire games without being identified by anyone else in them. But the way the new Thief game is being pitched, with Garrett as a simmering anti-hero, means we may be about to learn a lot more about him. He even has a catchphrase. "What's yours... is mine." That's what he purrs self-confidently as the new logo lingers on-screen at the end of his first outing for the press. Please adjust your gamma slider until the hashtags are barely visible.

Reinventing Garrett What do The Joker, Brandon Lee, a raccoon and an outlaw have in common? They all went into reinventing Garrett. Game director Nicolas Cantin talked in detail about the process and we document it for you elsewhere in our Thief coverage.

If you're a Thief fan retching at the sound of Garrett's contemporary makeover, however, don't get too worked up. At least not yet. There are definitely things here that you're going to react to with a certain amount of scepticism - I was the same - but Eidos Montreal has earned the benefit of the doubt with its confident handling of Deus Ex, and once you start peeling back the carefully staged Thief press demo and asking these guys questions about it, there's a lot to be encouraged about.

A lot of it can be summed up in a single scene: Garrett is on a rooftop in the midst of The City, on his way to break into a brothel called The House of Blossoms in pursuit of a nobleman wearing an expensive medallion, and in order to proceed on this path (others are available) he needs to bypass a couple of guards below him. Only problem: they're standing in a brightly lit doorway and one of them is facing outwards. Rather than waiting for them to move on, however, he does something awesome: he uses a rope to lower himself into the shadow behind the guard furthest from the door. What shadow? The dynamic shadow being cast by the lantern the guard is holding up in front of his chest. He then waits for the guards to move inside the door, follows slowly, and slips behind a stack of boxes to one side once they cross the threshold.

It's only a few seconds of gameplay, but it captures a lot of what sets this Thief game apart from the ones it follows: 1) Garrett is much more lithe and acrobatic and has new abilities, in this case a grapple-style device called The Claw that allows him to latch onto certain objects in the environment. 2) This is still a dark, tense game of stealth. And 3) this is a next-generation game, using the extra power of high-end PC, PS4 and the new Xbox to give the series a new hook. In this case, the shadows that were once baked into the environment to create avenues for stealth are no longer fixed - they move. I find the implications of that alone pretty exciting.

Sound of the underground Considering we got to speak to a lot of people - designers, artists, writers and engineers - and given the series' background, it was strange that the elaborate presentations we saw didn't focus more on Thief's sound design. After all, that's one of the first things people compliment about the other Thief games. Under questioning, the developers say it's still a big part of what they're doing. "You're right that it's crucial," says producer Stephane Roy. "It's really, really, really, really important for us. For of course the ambience but also the type of game. Just imagine the diversity in the 'barks' also with the AI - with the next-gen we have the possibility now that the barks will be really connected with the action you do. So the NPC won't look like they say something so generic that it's almost a joke, you know?" "It's a very discreet feature," adds lead level designer Daniel Windfeld Schmidt. "Fans of the old Thief franchise will recognise in the demo you saw earlier that there are carpets, and the carpets actually change the way, you know, if you're running you will not make a lot of sound. So this is more for the fans. In some places you'll think, wait, there's a full patch of light here but there's carpet, so I can run, so I just need to time it with the window of that guard looking every once in a while. We want that level of depth to the gameplay so it's not just waiting and then sneaking, waiting then sneaking; it's more about whether you can see the opportunities within the environment."

The dynamic shadow being cast by the guard's lantern is solid enough for Garrett to lower himself into it and remain concealed from view. As long as he stays within that shadow as the guards move, he won't be visible to anyone.

The developers are showing off a lot more than just those few seconds, mind you - the House of Blossoms demo is half an hour long and is designed to portray the gameplay loop Eidos Montreal has been working towards: creative and stealthy infiltration; nimble thievery, often with a bit of puzzling; and then a daring escape. The latter - as with the rest of the game - can involve as much audience interaction as you want. If you like taking people out and looting at your leisure, that's an option. If you like massive fights, go for it. And if you're like me and your preferred approach to stealth games is 'no touching', you can be a ghost.

The demo shows a bit of everything. There's an initial scene-setting trip into the heart of The City tucked under a blanket in a cart - an opportunity for a monologue from Garrett and a few scenes showing the oppression going on in the hub world where he lives, where bad guy Baron Northcrest's enforcers are throwing people in stockades and hanging them from buildings. Meanwhile, beggars and plague-ravaged citizens hobble around in the gutter under their boots. When Garrett emerges and the player takes control, he immediately overhears a couple of guards discussing the House of Blossoms and his potential prize - the wealth of a rarely seen aristo called Eastwick - and then he's off to work.

It's first-person for the most part, although the action sometimes shifts to third-person to highlight Garrett using the claw, clinging onto a ledge or performing an optional takedown on an enemy - reminiscent of Deus Ex: Human Revolution and, you know, all games with takedowns.

In the scenes that follow, we also see his new Focus ability, which can be used to identify things in the environment (ledges, breakable objects, loot) and to speed up actions (combat, lockpicking, pickpocketing). Unlike similar abilities in other games - I'm thinking Detective Mode in Batman Arkham and Dark Vision in Dishonored - you can't use Focus constantly and it will not recharge on its own, but it's there as an option for players to use tactically. It sounds like you'll be able to collect resources in the world to top it up.

Garrett also digs out his old blackjack, useful for clobbering guards (either in the face during fights or on the back of the head to avoid them) and this time it's going to be upgradeable, as will your Focus abilities. We also see Garrett's new collapsible metal bow, along with a pair of arrow types - broadhead and dry ice - with many more yet to be revealed. Broadhead is useful for headshots and dry ice for snuffing out lights.

Combat looks intimate and brutal. When you employ Focus in combat, you can drag a cursor over body parts in slow-motion to tag them and perform attacks.

As Garrett moves around, his level of visibility is indicated by an expanding circle in the bottom-left and by the varying tint of the wispy smoke that wafts around the edge of the screen, a bit like a damage indicator. When the smoke wafts darkly, he's concealed and when it flashes white he's out in the open.

We also get to see new ways of traversing the environment, like a dash ability that lets Garrett move between two adjacent areas of shadow without anyone noticing his movement. Think of it as a slightly more elegant first-person take on the cover-switching forward-roll that Gears of War invented and everyone else borrowed.

Helping hands The new Thief makes obvious concessions to players who have been brought up on gaming in the nine years since Deadly Shadows - for instance, when you're navigating narrow beams you will be guided along them automatically and dismounting will require you to press a button. But what about more old-school crutches? Noticing that the game auto-saves at various points, I ask whether quick-save/quick-load would be in. "We're still working on it," is the answer. Will there be a map? Yes, and it will be a bit more useful than the old ones. (Personally I liked the fact the old map was a bit useless, but I guess not everyone did.) There will be a mini-map, too, and while they haven't settled on how exactly it will work yet, it sounds like it won't highlight loot and enemy positions. Oh, and while there's no cover system, you definitely can lean and you'll definitely be concealed when you do. Bravo.

It's worth reiterating at this point that all of this is stuff you can do rather than stuff you have to do. Eidos Montreal is keen to press tools into your hands, but the developers stress that it's up to you whether you use them. For instance, there's a free-running section where Garrett bounds through a marketplace and does parkour tricks over benches and stalls, which is sure to wind up those of a sensitive disposition, and while in the demo it's staged in such a way that it feels unavoidable - Garrett has until the clock strikes 12 to reach the House of Blossoms, so he legs it - when I ask about it later I'm told you can break into the House other ways if you choose to dawdle instead.

It's inside the brothel that the game starts to more closely resemble the Thief we know, too. Patrons and their consorts for the evening are wandering around, some are draped over couches and falling into side rooms, and the resident Madame, Xiao Xiao, apparently has a strongbox somewhere, while there's also Eastwick's location to uncover and lots of juicy loot resting on shelves and other surfaces.

Moving nimbly between shadows, Garrett picks a few pockets and locks, avoids the gaze of half-slumbering lords and courtesans, locates a back room where there's some sort of ventilation system that can be laced with opium, and generally sneaks around performing the business we expected: thievery. Every time he loots an item, like a pocketwatch or a necklace, he holds it up and gives it a quick examination before thrusting it into the folds of his clothing.

We only get to see one path through it in the press demo, but the House of Blossoms looks like a large area with plenty of routes through it, and there's evidence of various side rooms to explore.

Even in the compressed timespan of this press demo, I can already see how a lot of my game will be spent: watching, waiting, making plans, acting them out, adapting to circumstances. When Garrett gets to grips with Xiao Xiao's strongbox, for example, he's disturbed while he's trying to pick the lock and has to conceal himself as the Madame uses a nearby mirror. When she disappears into an adjacent room to scold a subordinate, Garrett then investigates how Xiao Xiao actually came to disturb him, because it wasn't through the main door - it was through a secret entrance behind a bookshelf. Once he locates the switch, a concealed staircase takes him down into passages that allow him to stare through peepholes into rooms being used by the brothel's patrons.

It's here that the merest hint of the game's story emerges, too. Garrett catches Eastwick through one of the peepholes and discovers the nobleman scouting his private room for some sort of hidden symbol. After sneaking in and relieving Eastwick of his medallion, he sees a number of glyphs on movable concentric circles on its reverse, and uses Focus and other nearby peepholes to identify matching glyphs on the walls of the other private rooms. Inputting these into the medallion device starts something within it - it thrums to life and glows blue-white with some mystic power, something to which the game will inevitably return.

Dishonored, anyone? The developers make no secret of the challenges they faced developing Thief. It's clearly taken a long time and they didn't get it right at the first attempt. But one of the biggest potential threats ended up coming from elsewhere: Arkane Studios' Dishonored is one of the best Thief-inspired stealth games in the last decade. Having seen the new Thief in action, though, I didn't feel much overlap with Arkane's work. Dishonored is a brighter, oil-on-canvas vision of a steampunk Victorian city in decline, whereas Thief is all charcoal and smudging. And while both games have a rat plague, it's pitched as central to the plot and gameplay in Dishonored, whereas in Thief the rats are more of a surface detail, there to accentuate the social divide between the richer citizens living in Victorian-style accommodation and the poorer have-nots mired in a medieval kind of squalor. The games do have some things in common, though. The two things that stood out most were the promise of lots of secrets throughout your environment and a strong sense of verticality. Garrett's agility and claw tool often help him into the rafters or onto rooftops, perhaps not so readily as Dishonored's Blink, but with similar effect and intent. The other thing both games have in common is that it's difficult for a stealth-loving gamer like myself to look at them and not desperately want to seize control.

It's tough to form a rounded impression of Thief from all of this. For a start, it's got 'vertical slice' written all over it - I can just as easily imagine this stuff failing to make it into the shipping game as anything in the famous BioShock Infinite E3 2011 demo, the contents of which can be seen in various forms throughout the final game but never in the same order or density. The Thief demo gives us a roadmap for the team's hopes and dreams, which is fair enough, but it might not be completely representative.

As for what's on that roadmap, there's lots of good stuff, a few things I could take or leave, and other parts I hope they allow you to turn off. For instance, Garrett has Lara Croft's annoying habit of talking about what he's doing in such a way that it spoils moments of discovery in favour of making sure you know exactly what to do. "I wonder if there's one in each room," Garrett says after finding his first medallion glyph. Oh well gee d'ya think?!

But talking to the people making the game is more reassuring. When I mention that I wish Garrett kept some of those thoughts to himself, they seem genuinely concerned and promise to look at it. They tell me his cynical commentary as you play is a big part of the character for them, but they clearly don't want to put people off by over-explaining things.

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They've also worked in some artful touches, putting Garrett's hands on-screen as often as makes sense - gripping the edge of an archway as he peers round it, visibly steadying himself on moss-covered walls as he descends a staircase, and always coveting his loot before it disappears from view. They say they want to make the world more tactile, and while it's hard to judge that while watching someone else's playthrough, it's a good ambition.

Is Thief coming out on the next Xbox? Until Microsoft officially acknowledges that there even is a next Xbox, developers wishing to show their next-gen games to the press and public have to go to farcical lengths to obscure the fact they are working on it, lest they break their smothering NDAs. Microsoft's lawyers will be pleased to hear that Eidos Montreal kept their open secret throughout the Thief reveal event. Besides the confirmed PC and PS4 versions, "other next-gen platforms" is all we heard. However, there were plenty of signs that Thief is destined for the next Xbox, codenamed Durango - not least of which was the fact that we were shoulder to shoulder throughout the press event with senior writers from dedicated Xbox magazines. Unless they were there for their health, it seems safe to put two and two together.

Another thing I like is the talk of giving your enemies credible AI. Eidos wants to break the cycle of stealthy players screwing up and refusing to continue, so if you are spotted then the hope is you can derive pleasure from evading capture rather than going back to your last save or checkpoint. One way of encouraging this is guards who carry out systematic searches - rather than just probing areas repeatedly for the duration of a cooldown - allowing you to move into shadows they've already investigated in order to regain your anonymity.

It's these details that linger in my mind after I fly home, which is an encouraging thought, because it could easily have gone a different way. After Deus Ex, Eidos Montreal has given itself another tightrope to walk, and there was always the risk of tumbling into the fires of expectation raging across the internet once Garrett broke cover. Instead, I feel as though Eidos and Garrett are making good progress: Thief presents a slick, night-stalking anti-hero in a city of pain and depredation that I want to explore further.

There's still a long way to go to the other end of the tightrope, of course, but on the evidence so far I'm wishing them all luck.

Thief's just been released, and we've got an essential walkthrough to help you sneak your way through the game.