Malignant director James Wan has explained the scientific origins behind the film’s extreme ending.

• READ MORE: ‘Malignant’ review: James Wan’s bold and batshit haunted house horror

The film represents Wan’s return to horror after 2018’s Aquaman, with his previous spooky credentials including The Conjuring and its sequel, Saw, and the Insidious franchise.

Malignant might be his most bonkers project yet, with the ending particularly causing a stir among viewers for its elaborate concept – which is inspired somewhat by actual science.

The film opens in 1993, as scientists experiment on an unseen subject called Gabriel. This subject goes on a killing spree, leading scientist Dr Florence Weaver (Jacqueline McKenzie) to warn her colleagues about Gabriel’s power and ordering them to “cut out the cancer”.

In the present day, we follow Madison (Annabelle Wallis) who, after being slammed against the wall by her abusive husband Derek, starts suffering visions of a dark figure murdering people around Seattle, who kills Derek and Dr Florence Weaver.

In the third act, it’s revealed Gabriel is the killer and is actually a parasitic twin, a sentient form of a germ cell tumor called a teratoma. This was attached to Madison as a youngster, which Weaver’s team “cut” away all those years ago – leaving only a part connected to Madison’s brain.

After she was struck by Derek, ‘Gabriel’ was essentially reawakened within Madison – hence why she had the visions of the murders, because in the physical sense, they’re the same person. Gabriel, by periodically taking over Madison’s body, was killing those who had wronged him.

Speaking to Entertainment Weekly, Wan revealed how this twist, while stretching the facts, is inspired by some scientific reasoning: “My wife, Ingrid [Bisu], she does a lot of research into medical anomalies. She goes, ‘There are people that are afflicted by this thing [teratomas], that were born like this.’

“I just thought, wow. So obviously my horror movie-fucked mind went immediately to the most messed-up story I could come up with. Her and I, we just started spitballing ideas and [it] eventually snowballed into a concept.

“The whole time I was thinking, how do I take this seed of an idea and actually turn it into a film and what I can do with that can possibly allow me to have fun with all kinds of practical effects that I haven’t played with in a while? You know, the blood and guts and all the cool animatronic stuff. It stemmed from all kinds of aspirations, but that really was the start of that idea.”

Malignant is co-written by Wan, Bisu and Akela Cooper. In NME’s five-star review, the film’s described as “the best horror film of the year so far” which shows “what James Wan is truly about”.