It’s almost upon us, with a premiere at Cannes a few days before a simultaneous worldwide release on May 22, but Indiana Jones and the Kingdom of the Crystal Skull is a mystery. There is a television trailer for the film, and now a cinema one, but just a handful of stills have been released, and there have been no clues whatsoever about the plot. The action is set in 1957, the baddies are Russian, the object of the traditional quest, this time, is a powerful crystal skull. That’s about the sum of what Steven Spielberg, the director, and George Lucas, the producer, want fans to know.

Spielberg and Lucas are taking huge gambles on this fourth Indiana Jones movie. Big-budget sequels are seldom released more than a couple of years apart these days, but it’s been a full 19 years since Harrison Ford last put on his fedora and cracked his bullwhip, in Indiana Jones and the Last Crusade. Most of the youthful audience at which Hollywood aims its movies today weren’t even born then. And whoever heard of having a 65-year-old actor - which is how old Harrison Ford is now - as the star of a bone-crunching action movie?

The film-makers have taken other gambles. Spielberg decided early on that he wanted the film to have a distinctly old-fashioned feel. He and his cinematographer, Janusz Kaminski, watched the three previous films so they could match their style, itself based on the cliffhanger Saturday-matinée serials of the 1930s, 1940s and 1950s. (Douglas Slocombe shot the first three Indy films.)

“Both Janusz and I had to swallow our pride,” Spielberg says. “Janusz had to approximate another cinematographer’s look, and I had to approximate this younger director’s look that I thought I had moved away from after almost two decades.”

To achieve this look, Spielberg deliberately used few computer-generated shots and employed much less fast cutting than most modern action movies feature. Spielberg says he wanted to keep much longer shots than modern audiences have become used to in films such as the Bourne series, which he says he admires, because, “every time the camera changes dynamic angles, you feel there’s something wrong, that there’s some cheating going on”. Partly that’s because, for all the action, the Indy films are also comedies, and Spielberg wanted “to do the shots the way Chaplin or Keaton would, everything happening before the eyes of the audience, without a cut. To get the comedy I want, you have to be old-fashioned”.

Spielberg and Lucas also took a decidedly old-fashioned approach to the marketing of the film. While whole new divisions of studio marketing departments have grown up to exploit the attention movies now get on the internet, Spielberg and Lucas have done everything they can to try to make sure people will know as little as possible about the film when they file into the cinema. Extraordinary measures have been taken to keep the script a secret. Shia LaBeouf had to read the script in Spielberg’s office, while the director flew over John Hurt’s to the UK when Hurt insisted on reading it before signing on to do the film - and flew it back to LA on the next plane.

Despite their best efforts, which included everyone connected with the film signing cast-iron agreements not to divulge anything, aspects of the story have seeped out. One extra playing a Russian soldier leaked key plot elements to a newspaper in Oklahoma. “Apparently, the Soviet army was searching for a skull in the jungles of South America, and Indiana Jones was searching as well,” said the extra, whom Spielberg is said to have had digitally removed from the film as punishment. “We took Indiana Jones hostage and managed to find the skull.”

It has taken a long time to get a story that everyone - specifically Lucas (whose original idea Indy was), Spielberg and Ford - could agree on. The first script was written in the early 1990s and was called Indiana Jones and the Saucer Men from Mars. Lucas’s idea was that, as the first three films had replicated the movie serials of the 1930s and 1940s, with their emphasis on Nazis as villains, the fourth should take its ideas from the serials of the 1950s, when there was much more emphasis on space and aliens. But Ford didn’t like it.

Over the years, five other writers wrote treatments or scripts, the closest to getting made being one by Frank Darabont (who wrote The Shawshank Redemption). It was Darabont who brought back Marion Ravenwood, among other story elements that have remained in the movie. Spielberg loved the script, but Lucas, who has power of veto over such things, didn’t like the story, much to Darabont’s fury. He called Lucas “insane” for rejecting it and provoked much internet ire against Lucas, who is almost universally derided for the incredibly clunky scripts he wrote for the recent Star Wars movies. In the end, the writer to get the script credit on the film was David Koepp, who had co-written Spielberg’s 2005 film War of the Worlds. Koepp put the emphasis on what Lucas was interested in, the mythology of “crystal skulls”, which Ford calls “the mysto-crypto stuff that’s part of every Indiana Jones movie”. Ford’s voiceover in the latest trailer makes it clear that possession of the crystal skull is the MacGuffin – the narrative device – that drives the movie. “Whoever returns the skull to the city temple will be given control over its power,” Ford intones.

The leaks apparently quite depressed Spielberg, according to Lucas, who has said he told his friend audiences would not be “coming to see the plot. They’re coming to see Steve Spielberg interpret a story. You can’t get that any other way than by seeing the movie”. Which, of course, millions of us will.

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