Butch Cassidy to ride again – but this time the Kid gets left behind

Sequel will begin years after shootout that killed Sundance

The old swagger has become a hobble, and his famous sidekick is no more. But 40 years after his last brush with notoriety, a gun-toting villain called Butch Cassidy is about to delicately ease himself back into the saddle.

An elderly version of the celebrated Hollywood cowboy will ride again next month when shooting commences on a new film charting his tea-time years. In the absence of his previous alter ego, Paul Newman, the rakish Cassidy is going to be played by Sam Shepard. This time, sadly, he won't be running with the Sundance Kid.

The forthcoming movie, Blackthorn, will pick up several years after its predecessor left off, following an ageing Cassidy's attempts to pull off one last robbery that will allow him to return home from Bolivia to the United States.

This film has the Wild West outlaw somehow managing to survive the frenzied shootout at the end of Butch Cassidy and the Sundance Kid, and now living incognito with a native Bolivian woman, breeding horses and hiding his real identity, for roughly 15 years.

He's persuaded to return to crime by a young engineer, played by the Spanish actor Eduardo Noriega, who has robbed a local mine and is also on the run from the forces of law and order.

The film's writer and director, Mateo Gil, who won an Oscar for The Sea Inside, has described the rebooted Cassidy as "that tired and lonely old man who, for an instant, recovers all his energy and dreams due to someone who seems to reincarnate the past, his old friends and ideals".

The film will be shot on location in Bolivia and is pitched as an old-fashioned Western. "One of the things that I like most about Westerns is that it's a truly moral genre," added Gil, in a statement on the website of the production company, Arcadia. "The characters face life and death, and other very important matters (freedom, commitment and loyalty, courage, treachery, ownership and money, justice, friendship and even love) in very pure and simple terms. It's a genre that helps us look at our own life and find a way to face it."

Gil did not explain exactly how Cassidy managed to survive the final scenes of the 1969 film, in which Newman and Robert Redford are caught having a meal, take refuge in a house and emerge with guns blazing only to meet volleys of fire from a troop of Bolivian soldiers, and, seemingly, an inevitable death.

But the history books do give him options. Experts have always been divided about what happened to the real Butch Cassidy, who was born Robert LeRoy Parker in Utah, in 1866, and became one of the old Wild West's most famous train and bank robbers.

Parker led a criminal gang called The Wild Bunch, and after becoming one of the country's most wanted men, disappeared to South America with one of its members, The Sundance Kid, whose real name was Harry Longabaugh. Some historians believe the duo were killed during a shootout near San Vicente in Bolivia in 1908, which is the event depicted in the final stages of Newman and Redford's film.

Since their bodies were never formally identified, others believe that the famous 1908 shootout actually involved two completely different people, and therefore reckon that the real Cassidy managed to return to the US, where he lived incognito for several decades.