Heretic ending explained: Full spoilers for Hugh Grant horror film

However after Sister Barnes (Sophie Thatcher) and Sister Paxton (Chloe East) arrive at his home, it quickly becomes clear that he has some sort of ulterior motive. He almost instantly behaves suspiciously, appearing reluctant to introduce them to his wife who he promises is in the next room, and before long is theatrically lecturing them on the nature of religion with help from some slightly unorthodox examples.

As Sisters Barnes and Paxton become increasingly alarmed about what he has planned and whether they'll be able to make an escape, the tension ratchets up until some major left-field twists late in the run time.

Seen the film and need a recap of those closing moments? Read on to have the Heretic ending explained.

Heretic ending explained: Full spoilers for Hugh Grant horror film

As Mr Reed chats to Sister Barnes and Sister Paxton it soon becomes clear that he was never in any way interested in converting to Mormonism – but that he has in fact laid an elaborate trap for them.

Although he repeatedly assures them that nothing sinister is going on, his actions suggest otherwise. For example, it emerges that his wife is not actually real, he had simply placed a blueberry pie scented candle on the table to add credence to his lie that she was baking in the next room.

Anyway, as the missionaries come to terms with the increasingly alarming situation they find themselves in, he continues to babble on about faith and how he believes all religions to be nonsense – apart from one which he mysterious calls "the one true religion". He talks about "iterations"– making analogies to everything from Monopoly to Star Wars to Radiohead's Creep – to show that most religions have simply been adapted from each other.

Eventually, after revealing that there is no other way to exit the house, he gives them a choice of two doors to go through – one for if they still believe in their Mormon faith, and another for if they will admit that he is speaking the truth.

Sister Paxton – presumably believing this is the best way out of the situation – decides that she will go through the door marked disbelief, but Sister Barnes refuses to join her and argues against some of Mr Reed's points. And so the pair of them end up going through the belief door.

This is where things begin to get really weird. The door leads to a dingy basement and when they climb down the stairs they find a very haggard looking old woman, and Mr Reed tells them that she is a living prophet who can perform a miracle.

He feeds her a pie – blueberry of course – and then tells Barnes and Paxton that it had been poisoned, which causes her to drop dead. But he then lets them know that she will resurrect and tell them what she saw on the other side in the brief time that she was alive.

At this point there's a ring on the doorbell and Mr Reed goes to answer it – to find that the Mormon elder is looking for the missionaries after they did not report back.

Unfortunately, he is perfectly satisfied with Mr Reed's claims that he hasn't seen them, and so this possible rescue attempt doesn't go anywhere. But while he was away, Barnes and Paxton tried to think about other ways to escape and manage to get their hands on some matches and try to start a fire to create smoke signals and alert someone to the fact they are trapped.

Anyway, in the. midst of this, the old woman appears behind them and does just what Mr Reed had said she would, explaining that she saw clouds and angels during the time she was dead – before cryptically saying that "it isn't real".

Reed then arrives back in the basement, and after some arguing with Barnes and Paxton very suddenly takes a knife out and cuts Barnes's throat, apparently killing her – although Reed claims that this will be another miracle and she will come back just like the supposed prophet.

When it appears that that isn't happening, he then cuts into her arm and takes out a piece of metal which he claims proves that Sister Barnes wasn't actually real and that the world is a simulation. He then tells Paxton that the only way she can escape the simulation is by killer herself, as she is real and this will take her back to the real world.

But Paxton is not convinced. She says that the piece of metal is actually a contraceptive and that Reed is just trying to come up with an excuse because something in his plan has gone wrong. Meanwhile, she also puts forward her own theory about how he pulled off the trick with the prophet...

What was Mr Reed's plan?

Paxton explains that Reed had simply switched out the dead woman, making use of the doorbell distraction – which he had factored into his plan – to get another woman to get rid of the body and take up the same pose, before reading a script about what life is like on the other side which Reed had provided her.

But she went off script, with her comments about how it wasn't real, which forced Reed to improvise the simulation part of his plan. Paxton then finds a hatch which leads to another cellar, and she goes down there to discover there is a room with loads more women who all look similar to the prophet and are being kept in cages.

Mr Reed then follows her down and asks whether she has worked out what the one true religion was, and she replies that she has: it is 'control'. He had planned every moment – apart from the simulation part – to lead her to this moment, to prove that he can control anyone, in the same way that all religions do.

As he continues to explain this, Paxton then stabs him with a letter opener and runs back to the previous basement, but while she checks on the seemingly dead Barnes, the wounded Mr Reed reappears and stabs her in the stomach. She falls to the ground and starts praying, as Reed crawls towards her – seemingly to slit her throat and kill her.

But just as he's about to strike, he suddenly gets hit on the back of the head and falls over dead, and it turns out that Barnes hadn't been dead quite yet, saving Paxton with her final act before she too falls over and dies.

Paxton then returns to Mr Reed's study and manages to make an escape through a window to find that outside is now covered in snow, with the final scene showing a butterfly landing on her hand.

It's not made explicit exactly what this all means – and unlike Mr Reed, the film doesn't make any definitive statements about faith. But the final moments can certainly be read as a miracle, with Barnes managing to cling onto life just long enough to save her friend.

An alternative reading as that Paxton actually did get killed by Mr Reed, and what we see at the end is simply her entering the afterlife – with the now snow-covered ground representing the clouds that the prophet had spoken of earlier and Barnes re-appearance representing the angel. Just like with faith, it's up to the individual viewer to find the interpretation that makes the most sense to them!

Interestingly Hugh Grant recently revealed he filmed two separate endings for Mr Reed, telling Games Radar: "There's a moment where I crawl across the floor to her, having been stabbed, which I did in two ways. One where he's still trying to make the whole thing fun, as he's been trying to make the whole evening fun. He's kind of going, 'Look at this, this is fun, dying'.

"And then I did another one where all his defences have gone and he's absolutely sh**ting himself that he's going to die, and he's very frightened. He wants some comfort and he wants her to comfort him, perhaps with a prayer."

He added: "I am not entirely clear the way they edited it, which of those two performances they're going for. I think it's the latter. But I know they telescoped the last 20 minutes quite a lot, the film was running long, so maybe it's not quite clear. I quite like the second way – finally after a whole hour and a half of this guy totally being in control, he’s a frightened rabbit."

Heretic is now showing in UK cinemas.

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