I’ve been thinking about the difference between horror and thrillers, and how the two are often intertwined. It helps if we refine what ‘thrill’ means. It’s that surge of fight or flight energy that can be hugely exciting because it implies you have a chance to get away. Horror differs because it’s the dreadful feeling you have when you realise you can’t get away.

At the beginning of a horror story the protagonist might not realise they’re doomed, but the reader knows, and is interested to learn how the character reacts to the story beats that strip away external characteristics to find the person beneath.

The ‘final girl’ horror scenario – in which a solitary young female bucks the sacrificial trend and gets away – still follows this psychological pattern because the horror journey is undertaken by the characters who don’t make it. The earliest and best example of this story structure is Alien, which is a masterpiece of emotional characterisation.

Every one of those people is faced with the worst thing in the world for them.

Kane is a middle-class white guy who does a boring job but fancies himself as a hero. He usually gets away with the risks he takes because they aren’t very risky. When he goes down into the alien ship, he doesn’t expect to get impregnated with a chest-bursting monster because the thought of it is outside his limited experience. It’s actually outside everyone’s, but that’s not the point – he is the one who chooses this job because he thinks he will get away with it. That’s why his seeming recovery is so upsetting. He thinks he’s okay. He isn’t. It’s just a question of time.

Dallas is lazy and not very competent. He is older than Kane and is probably the captain because he looks like a retired quarterback. He doesn’t want to be bothered with any of this, which is why he lets Ash over-rule Ripley about quite rightly keeping the search team outside the ship. Dallas is the first to see the alien in its true form, and the timing, the lighting and the revelation are shocking. But there is another dimension to our emotional response to this twist. It’s that in another film, Dallas would be the hero because we’ve been primed to think that by shows like Star Trek where it’s the captain’s story. Everyone assumes Dallas won’t die, especially Dallas, and that glimpse of horror has a (very deeply hidden) element of ‘well that’s my weekend screwed then’. In other words, the job he has to do turns out to be much harder than he was prepared to undertake. Like Kane, Dallas has just been getting away with it for too long.

Lambert is a very sensitive, anxious person. Her body language, large frightened eyes and even the way her hair sticks up suggests she is in a constant state of fear. Even working on an advanced spaceship whose computer is called Mother does not comfort her. For reasons we will never know, Lambert has spent her life believing that something like the alien will get her. When it finally does, her death is one of the longest and most drawn out, because it feels like a realisation of her greatest fears. As a sidenote, it’s revealed in the sequel Aliens that Lambert is male to female transgender. The alien is a famously phallic creature, which adds another layer of horror to Lambert’s death. While no watching the first movie in 1979 would have known this detail, it’s a mark of quality writing that subsequent character revelation only intensifies the horror.

Parker is an angry man who hates being screwed over by the corporate world in general and management of the Nostromo in particular. He is also an engineer, so he’s used to things that make sense in a logical, mechanical way. There are three elements to his horror arc. One is that the company really is screwing him over, and sees him as even more expendable than he has spent most of his career believing. The other is that it’s a machine, the synthetic human Ash, who is responsible for letting the alien on board in the first place. The third is that while the alien has a logic of its own, it is also an agent of chaos, which Parker is ill-equipped to cope with. He is also brave – as brave as Ripley – and physically powerful. He tries in vain to save Lambert, who has to witness her colleague’s death before suffering her own. Parker is the only one who physically fights the alien. When he slowly loses it is the dread realisation that, like Lambert, his deepest fears were right all along. This dynamic is why their deaths take place in the same space when the others all die alone. It’s not enough to be destroyed by your own personal horror – you must have a witness as well, like a mocking echo.

Brett is a laid back, gentle man who quietly gets on with things. He has spent his life keeping his head down and out of trouble, despite Parker’s literal machinations to reduce their workload by pretending there’s something wrong with the coolant system to get Ripley off their backs. It is fitting that when Brett looks for the alien in the hold that he thinks he is searching for something the size of a cat. That is the scale he thinks at. He knows there are bigger, scarier things out there but believes that if he manages not to get involved then they will leave him alone. Even when he finds the cast-off skin of the juvenile alien, the reality he now faces either doesn’t occur to him or – more likely – he deliberately avoids thinking too much about it. Again, his death scene is beautifully set up, both in terms of characterisation and thus suspense. Something is leaking water down in the hold. A dedicated engineer would sort it out, but Brett doesn’t because he hasn’t been told to. Instead, he takes his cap off and stands under it, a moment of sensual abandon in the high tech but dilapidated ship. But it isn’t just water up there, and Brett’s dying screams are very different to Lambert’s. There’s a tone of grief there, of resignation, as if he has been betrayed.

Ash is all about control. His whole character is a masterclass of understated snobbery. Like Kane he is English (the rest of the crew are American), so he understands the nuances made available by education and status in a very particular way. The scene where he puts Ripley in her place by asking her not to touch things tells us all we need to know about both of them. He knows she is a stickler for the rules, he just has to remind her of them. His admiration for the alien is based on appreciation of the same efficiency he utilises all the time. HR Geiger described his aesthetic as ‘biomechanical’, which links the alien to the android in another way than just the central conspiracy. In both cases, what we initially see (a repressed English scientist, a large egg) does not represent the actual threat. And yet Ash is defeated by the humans he despises so much. Reduced to a talking head dribbling milk like an infant – which is a link to the computer Mother again – he never gets to see his mission completed.

In the same way that the threat is only gradually revealed, so too is the protagonist. Ripley starts off understated, a bit bossy, and is actually quite dull because why wouldn’t she be? She is middle-management and no one listens to her. If they did, the story wouldn’t even happen the way it does. The film nails gender politics as well as it does class conflict, and her initially adversarial relationship with Parker resolves into genuine understanding when they join forces. That resolution works because both of them know they are not really respected. They respond to this in different ways. Parker plays up by misquoting company regulations and pretending things are broken when they’re not. Ripley just keeps on, never losing her temper despite her obvious frustration. There’s a racial element at play here too. As a Black man, Parker knows that he has less leeway than Riplay, who is white. That is why she is the last one standing, and not him. He already knows the odds are over-stacked against his success in life, even before the Nostromo lands on the planet and picks up the alien. Ripley doesn’t, which is why she keeps arguing with the senior crew. In other words, Ripley doesn’t think she will ultimately fail. She is a company woman who thinks things should be done properly and – beneath all that – is deeply compassionate (she goes back for the cat). And yet not only is her crew wiped out, her ship is destroyed as well – for nothing because the alien has got aboard the escape shuttle with her. The scenes where she tries to deactivate the self-destruct system as amid blasts of steam and the dispassionate computer voice are hard to watch, but the tension comes as much from facing her worst fear – failure – as from our hard-earned emotional investment in her visceral need to survive.

Each of these characters is doomed from the beginning of the story, in most cases by death and in one by failure and then a kind of living death. The sequel reveals two tragic truths – one that Ripley drifts for over half a century, and the other that she is a single mother who outlives her daughter. These compounded horrors, and those that make up the rest of Alien, only work because more than the scary monster – itself a great character – the story has both understanding and a big broken heart.