Joker spoilers lie within...

In Todd Phillips' harrowing Joker, the disintegration of Joaquin Phoenix's failed clown Arthur Fleck is laid uncomfortably bare.

Part of his delusional behaviour, as it transpires towards the film's final act, is that he has invented a relationship with Zazie Beetz's single mother Sophie, who lives in his apartment building.

In the pivotal scene, Sophie is shocked to find Arthur in her apartment, and it soon becomes clear that she barely knows him, and that previous scenes in which he and Sophie have been friendly are all in his mind.

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But movie-goers have been debating much of what happens next.

Arthur leaves the apartment, but Sophie's fate is left ambiguous, particularly given Fleck's recent descent into murderous behaviour.

According to the movie's cinematographer Lawrence Sher, however, she does not come to any harm.

“We wanted to make the interpretation of the real versus what’s not real, a part of the viewer’s experience,” Sher told Slashfilm.

“For instance, his relationship to Sophie is a fantasy to him. Some people have asked me, ‘Was she killed?’ Todd makes it clear she wasn’t killed.

“Arthur is killing people who’ve wronged him in a certain way, and Sophie never wronged him.

“In terms of what we did visually to play with the real and not real, there are callbacks and scenes that mirror each other.

“We leave hints using imagery or way we covered scenes similarly between scene. Outside of that, I like that people can have the conversation and come to their own conclusions.”

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To be fair to audiences, Phillips does not make it explicit that she wasn't killed, by cutting to the apartment block hallway rather than seeing him actually exit the apartment with Sophie still alive.

The movie is heading rapidly for the record books, and will likely top out having made well over $900 million at the box office, a huge sum for a movie that cost around $70 million.

According to reports, it will likely make around the same amount of profit for Warner Bros as Avengers: Infinity War did for Disney.