Dead of night, and on a deserted Florida landing strip, the silence of the oppressively hot early hours is broken by the low whirring of an electric golf cart, driving lazy circuits.
At the wheel is a bulky, lone figure, hunched forward over the controls as he tries to kill time during another long, sleepless night.
It is a sight that has become something of a regular occurrence in recent weeks, as Hollywood star John Travolta acts out his bizarre nocturnal ritual on the private runway that services his Jumbolair estate.
'We often see John driving himself around at night,' one of Travolta's neighbours told me this week.
'It's sad to see. You rarely catch sight of him during the day. We used to see him driving around on a buggy with his son. Now it's just John by himself. He's always been a night owl, but now even more so.'
But then Travolta has much on his mind. Six months after the tragic death of his only son, Jett, during a family New Year holiday to the Bahamas, he is said by his closest friends to remain in a state of almost constant distress.
Work has been cancelled, the shutters pulled down, and until a rare appearance in public this week, the actor had been living the life of a virtual recluse.
His friend and fellow actor Denzel Washington, who appears with Travolta in the upcoming thriller The Taking Of Pelham 123 - which was shot before the tragedy - gave an indication of the depth of his co-star's despair: 'One minute he's OK, the next he's in tears. He's such a sweet, sweet person.'
Certainly, those around the Pulp Fiction star are privately concerned about his state of mind.
And Travolta cut a miserable figure when he was spotted for the first time in months on a flying visit to Miami this week.
The 55-year-old actor, who was sporting an eccentric handlebar moustache and a shapeless, baggy shirt, looked bloated and puffy. He hid under a black baseball cap as he ate an unhealthy lunch of cheeseburger and chips alone outside a fast-food joint.
Few would blame the formerly lithe Saturday Night Fever and Grease star for over-indulging his long-time love of junk food as he struggles to come to terms with the death of his 16-year- old son, who died after suffering a seizure at his father's holiday villa.
But if rumours buzzing around Hollywood this week are to be believed, it's not just the death of his beloved son that has been torturing Travolta of late.
His distress, say sources close to him, has been compounded by the first cracks in his 34-year relationship with the Church of Scientology, the cult-like religion of which Travolta is a prominent and generous benefactor.
And there are dark mutterings that if he carries out private threats to leave, the organisation will go public with embarrassing details of his private life, including, it is claimed, allegations of past homosexual relationships.
Sources in the U.S. disclosed to me this week that his son's sudden death has 'deeply shaken' Travolta's faith in the strange sect, which makes wild claims about its ability to cure a variety of physical and mental disorders.
The star - who, thanks to his dedication and open cheque book, has risen to the top of the secretive organisation - is said to be angry that the religion was unable to help Jett, who was widely reported to have suffered from autism.
'There have been strong rumours coming out of Scientology that John Travolta is disappointed that the religion was not able to help his son more,' Rick Ross, an American author and lecturer on Scientology, told me this week. 'It's led him to question his faith.'
Travolta is also said to be upset that senior members of the sect have instructed him to undergo intensive sessions with one of Scientology's 'ethics officers', trained to question the actor and other grieving family members to establish whether their 'negative influences' might have contributed to the tragedy.
But there is much more to this than just a questioning of a once rock-solid faith. 'I think it would be very difficult for John Travolta at this stage, given his history with the religion, to extricate himself from the Church of Scientology,' said Mr Ross, who has investigated the sect for almost 30 years.
'It would be a huge move on his part because Scientology keeps files on its celebrity members containing embarrassing personal information about them.
'And Scientology has proven in the past that it has a penchant for releasing that information to embarrass people who have left and who have said things it doesn't like.
'If celebrities leave, they tend to do it quietly and keep their mouths shut, because if they do speak out, they are opening themselves up to attack from Scientology.
'That's why I think Travolta will want to keep his problems with the Church private.'
Travolta's friends have been speculating among themselves for months that he now deeply regrets adhering so strictly to the cult's outlandish instructions over his son's medical treatment.
His sense of guilt is said to be compounded by his blind acceptance of the Church's claims that conditions such as autism do not exist, but are merely psychosomatic.
It recommends they are treated by detoxification programmes and vitamins, rather than conventional drugs.
Indeed, Travolta's wife, actress Kelly Preston, campaigns vociferously against psychiatric drugs and the family's lawyers have confirmed that Jett had been taken off the antiseizure-drug Depakote because, they say, it failed to work.
Instead, Preston 46, herself a committed Scientologist, is said to have enrolled her son on a Scientology-led Purification Rundown course.
This involved treating Jett with saunas, food supplements, Vitamin B and vegetable oils which, the sect claims, can dislodge toxins trapped in the body's fatty tissues.
Perhaps because Scientology does not recognise autism as a clinical condition, she and Travolta, who also have a nine-year-old daughter, Ella Bleu, instead claimed that Jett's condition, which rendered him virtually mute and caused up to four epileptic fits a week, was caused by the little-known Kawasaki Syndrome.
They claimed that the illness, which affects the heart and is not usually seen in children over the age of five, was caused by the carpet detergents that Travolta, who is obsessive about cleaning, insisted were used in his son's bedroom when he was a baby.
But now, it seems, the double Oscar nominee is doubting the wisdom of following Scientology's weird prescriptions.
Word of Travolta's loosening ties with Scientology is certainly a blow to the religion. He and fellow movie heart-throb Tom Cruise have been its two most significant Hollywood disciples.
Travolta is also known to have pumped millions of his own fortune into its new Superpower Centre, being built at Scientology headquarters in Clearwater, Florida.
According to insiders, he has reached the rank of Operating Thetan VII, one rung below the most senior position in the Church, which adheres to the teachings of controversial 1950s science fiction writer L. Ron Hubbard.
The author bizarrely claimed all humans are descended from Thetans, space aliens who were banished to earth 75 million years ago.
At great expense, Travolta turned another of Hubbard's novels, Battlefield Earth, into a disastrous 2000 film.
But to reach such an exalted level within Scientology, Travolta, insiders say, has had to submit himself to years of so-called 'auditing', during which disciples are connected to primitive lie-detectors and subjected to hours of questioning about their innermost secrets.
Perhaps unsurprisingly, given Hollywood's obsession with the secret sect, talk in the smarter salons of gossip-hungry Tinseltown is now all about what Travolta might have divulged during these sessions.
At the centre of this rather frenzied speculation has been his continued relationship with Jeff Kathrein, the fellow Scientologist whom Travolta was photographed kissing on the lips on the steps of a private plane three years ago.
Strangely, 29-year-old Kathrein, who is a wedding photographer from Florida, was described as Jett's nanny when it was revealed that he had discovered the boy's body on the floor of a bathroom in Travolta's £3million beach house in Grand Bahama last January.
It is not the first time that Travolta has been the subject of whispers about his sexuality.
In 2001, he was the subject of lurid claims that he had tried to pick up a business executive in a California health club.
The allegations came three years after Travolta was named as a homosexual in U.S Federal court papers, issued by a former member of the Scientology Church, who alleged the sect used the actor as an example of how gays could be 'cured' by the religion.
Earlier, the prestigious Time magazine also reported allegations made by Richard Aznaran, the former security head of Scientology, that the Church's leader, David Miscavige, had repeatedly joked about Travolta's 'promiscuous homosexual behaviour'.
Aznaran's claims came just months after the star was the subject of wild accusations in an American supermarket-tabloid that he had enjoyed a two-year affair with a gay porn star called Paul Barresi, who had a bit part in Travolta's 1985 flop, Perfect.
In the wake of Barresi's claims, Travolta - who at 37 was still a bachelor - announced his sudden engagement to Miss Preston, who was already a committed member of the sect and with whom he starred in the forgettable 1989 comedy The Experts. The couple married two years later.
The actor's only previous serious relationship was in the mid-1970s, with actress Diana Hyland.
She was 18 years his senior, but the couple moved in together after appearing in a U.S. television movie. Tragically, less than a year after they became an item, she died in his arms of breast cancer.
Despite the gossip, his marriage to Preston is one of the most enduring in Hollywood. Their three homes include a state-of-the-art £14 million Florida mansion, which was built to resemble an airport terminal and has parking for trained pilot Travolta's Boeing 707 airliner and two Gulfstream jets.
Despite this, Travolta has admitted that he and Preston have had to resort to years of marriage counselling to keep their relationship on track.
And while Preston has returned to work after the death of their son, Travolta has done much of his grieving in private.
In April, for example, he flew himself to Tahiti to spend time alone over Jett's 17th birthday.
To add to the tension, the couple are said to be dreading returning to the Bahamas at the end of September, for the trial of an ambulance driver called to treat Jett.
The man and his female accomplice are accused of trying to extort £12 million out of Travolta by threatening to go public with embarrassing private details surrounding the teenager's death.
Even so, sources told me this week that the couple are desperate to have another child. His friends can only hope that the prospect of a new life might finally lift Travolta out of his grief.