Corruption, deceit and murder. It's the late 1940s and the Second World War has come to an end. Hollywood's Golden Age is in full swing and LA is enjoying a massive economic boom. Yet, beneath LA's Hollywood glitz and glamour beats an impenetrably dark heart, where corruption, deceit and murder simmer beneath the surface. Welcome to LA Noire, Rockstar and Team Bondi's ambitious detective thriller set amid a violent period in La-La Land's chequered history, where you're a good cop entangled in the brutal crimes of a rotten town.

Cole Phelps, played by Mad Men's Aaron Staton, is the detective at the centre of LA Noire's tale. A decorated war hero, Phelps returns home and re-evaluating his life, he decides to join the LAPD and being recognised for his incredible potential, he's soon fast-tracked for promotion and working murder cases that take him deep into the city's seamy underbelly. During an extended hands-off demo of one of LA Noire's numerous cases, we start with a debrief from one of our superiors before selecting a case from one of the desks, each with their own selection of case files.

'Fallen Idol' is a case taken from the ‘Traffic’ desk, the first you'll experience having walked the streets as a beat cop. Coupled with Phelps' Traffic desk partner, Stefan Bekowsky, we climb into our unmarked car and ride out to a crash site, where a Chevy Styleline careered off the edge of an escarpment during a rainy night, hitting a billboard on the way down. It's 8:23am the next morning, and dispensing with a cup of coffee, Phelps and Bukowsky are right on the crime scene, where the coroner is on hand to help and the search for initial clues commences.

Immediately, you realise that LA Noire is a resolutely adult game, dealing with themes that you'd normally find in any mature movie thriller. The moment that you find torn underwear and blood spattered on the car's passenger side dashboard, you know that there's been foul play. You can pick up and examine any clues for further evidence and as you search, subtle audio cues keep you on track as some early hand-holding to ease you into LA Noire's mechanics. As the coroner hands you a bizarre shrunken head before you leave the scene, we see the manipulation at work, the pad gently vibrating should you spot something pertinent.

The head is a movie prop, which gives us our next lead, but not before Bekowsky suggests that we move on to question one of the crash victims, an actress by the name of June Ballard, who is at the scene being treated for minor injuries. Phelps automatically updates his notebook with a POI (person of interest) upon meeting new suspects or anyone essential to the case, making it an important tool for both keeping track of the case as it unfolds and for planning your line of questioning. Team Bondi's groundbreaking MotionScan technology also plays a substantial role in interrogations and you'll need to carefully gauge a person's behaviour, gestures, expressions and the inflection of their voice as you gather vital information and testimony.

Interrogating Ballard, we register that she's withholding something as she talks, moving her eyes around, visibly nervous as she responds to the line of questioning. Choosing from three dialogue options that are always the same, we can select X to Believe or Coax, square to Doubt or Force and triangle to Disbelieve or Accuse. In this instance, Phelps suspects that Ballard's holding back, so he calls her testimony into question, using the Force option, referring to the underwear as evidence to support our argument to draw information from her. There's no disputing the evidence, which gives us a name to follow: Mark Bishop. It's worth noting that every word of dialogue uttered is logged in a complete script that you can refer back to from the pause menu, so if you think you missed a salient few words, you can scan through the log whenever you please.

More questioning also reveals that the shrunken head - which it transpires was used to jam down the car's accelerator pedal - came from a prop house, warranting another scribble in the notebook. So far, it's clear that someone tried to kill Ballard and her passenger, Jessica Hamilton – a fifteen-year old girl with aspirations to become a movie star – and that both were drugged. It's time to question Hamilton and find out her side of the story.

8:36AM, Central Regency Hospital. Hamilton is awake and sat up in bed, but the on-duty doctor and Bekowsky remind Phelps that she's young and still in a delicate state, so we need to treat her with kid gloves. Being too heavy handed with your questioning can close a witness down completely, so cautious coaxing is advised where she's concerned. Again, we have to look carefully for tells and gesticulations to discern whether Jessica is telling the truth, but being too forceful is not an option. It soon becomes apparent that she was doped and abused, and that Bishop played some part, which hasn't become entirely clear just yet.

As we go to leave the ward, we catch sight of Ballard and so tail her car to a nearby café, where we take cover outside before sneaking in and hiding behind a newspaper. From here, we can eavesdrop on her phone call, revealing an address to check out. This time we let Bekowsky drive and use the 'trip skip' feature to fast travel to the next location, without missing important dialogue.

10:10AM, Wilson's Hotel. Nearing the building, dispatch radio a crime in progress at our location, in room 803 where we're heading. Ballard's husband's goons are roughing up Bishop's wife, Gloria, but we made it just in time to fight them off and send them packing. The melee system is still being refined, so the fighting looks a little off at present, but Phelps and Bekowsky manage to have them arrested and thrown into a paddy wagon. Had we been too late however, things might have turned out differently.

A few questions for Gloria, who is slightly cagey after her ordeal, gives us the address to the Silver Screen Props house and another name to pursue in Marlon Hopgood. We also learn that Mark Bishop has an unhealthy penchant for young girls, so we hotfoot it to the prop house to squeeze Hopgood for more, but not before phoning Records & Information for extra info on Silver Screen Props. Hopgood then folds under questioning once Phelps threatens to break his jaw and a search of the premises reveals a secret filming room, some chloral hydrate pills and an empty film can with Bishop and Hamilton's name. It turns out that Hopgood and Bishop were drugging young starlets and selling the sex films to burlesque houses.

The final section of the demo is all action, as we meet Roy Earle, a loudly dressed corrupt vice cop who's protecting Ballard's husband's mobster lackeys. Wise to our break in the case, the mobsters engage in a car chase, filling our glossy paintjob with bullet holes. There's a full vehicle damage model, and eluding the goons leaves our car in a wrecked state, minus hood and bumper.

5:30PM. Limping on to Bishop's movie set for his latest, titled 'Jungle Drums', we find the smut-pedaller on site and give chase on foot across a weak, splintering wooden scaffold. Nowhere left to run, he's ready to give himself up, but we have to escort him out alive under fire from more mob heavies. And with that, the demo ends.

'Fallen Idol' is just one of LA Noire's cases, but it demonstrates just how deep the game delves into the pitch dark and seedy side of LA's underworld. Things will apparently get more complicated and convoluted (in a good way) as you work through Noire's cases, according to Rockstar, and you'll find that locating the clues is only half of the battle. Knowing how and when to use them is the key to good detective work. That said, even the most ham-fisted detective can find a route to successfully solving a case, and there are no fail states in the game.

We also feel obliged to mention that Team Bondi's MotionScan facial capture is likely to be every bit the revolution that Rockstar promises it will be, capturing truly outstanding and natural performances from LA Noire's cast, making every other game's animation and lip-sync look remarkably primitive by comparison. This level of cinematic detail seems to extend to other parts of LA Noire too, the city itself appearing utterly authentic, and though not 100% accurate, it already looks like a pretty spot-on representation of LA in the late '40s, complete with real brands, advertising, landmarks and jazzy music. An evocative open-world with brains and brawn?

Let's hope that LA Noire can deliver in spring 2011. We've got the evidence to suggest that it will.