How Alfred Hitchcock kept the suspenseful plot of Psycho a complete secret

Thanks to Twitter, online reviews and industry leaks, keeping a movie plot shrouded in secrecy in 2017 has become an impossibility.

Back in 1960, however, things were very different.

Variety recently took a look back at Psycho, the movie that redefined the thriller genre, and the great lengths Hitchcock went to keep the movie's many shocking plot twists a secret, reports news.com.au.

A warning: Psycho spoilers below, if you haven't yet seen the film.

By today's standards, the movie's release was extremely slow, with screenings rolling out across the US, city by city, over the course of several months.

Despite that, the pivotal scenes of the movie remained a mystery for those who hadn't seen it.

Hitchcock himself had implemented numerous strategies to keep people from ruining it for others.

While it used to be common for viewers to walk into a movie halfway through and just wait for the next screening to see what they'd missed, Hitchcock knew that would ruin the suspense and the entire plot line of the movie.

Instead, he banned people from entering the theatre after the movie had started. Little did he know he'd also started a tradition that would become today's standard for moviegoers.

Janet Leigh was the biggest star of the movie but, given her shock early death in the film, Hitchcock didn't want viewers entering halfway through wondering why she wasn't in the movie.

Before Psycho's premiere, he called the demand for audiences to see the movie as a whole a "daring presentation policy".

Psycho was based on a 1959 book by Robert Bloch and, to avoid anyone finding out about the plot, Hitchcock purchased every single copy of Bloch's novel in circulation when it was released.

Paramount executives, the company producing the film, were also barred from reading the script.

Hitchcock had such a solid reputation by then that the studio agreed to give him $US800,000 (NZD $1,109,201) to create the movie, despite being left in the dark.

He didn't even shoot the movie at Paramount Studios, instead doing all of his filming at Universal.

But Hitchcock's demand for secrecy demands came at a price - he was forced to give up his usual salary.

It all paid off in the end: The profits from the movie ended up earning Hitchcock a huge $US6 million (NZD $8,319,009). Today that would equate to around $US50 million (NZD $69,325,077)