Even in late October, the heat in Corpus Christi shimmers on the streets, changing the perspective creating that little illusion of things not being quite as they seem.

The south Texas town normally enjoys the last of the summer tourists around now but this week has seen an influx of journalists, keen to find out more about the man at the centre of an Iranian backed plot to kill diplomats in the US.

The federal indictment says the 56-year-old Mansoor Arbabsiar who was born in Iran was recruited by elements of the country's Elite Al Quds Force of the Revolutionary Guard to buy the support of a Mexican Drug cartel to carry out an assassination in Washington.

But there's growing scepticism about the role played by the failed second-hand car salesman.

Arbabsiar moved to the US in the late seventies to attend university. After graduating, he boasted he was going to make lots of money but got involved in a series of businesses which failed or simply scraped along.

Some in the US media reported that his friends called him Jack because apparently the people of Texas found Mansoor too much of a stretch, too difficult to say. In reality he was given the nickname because of his love for a certain brand of whiskey.

The idea that the failed second-hand car salesman could be the lynchpin of such an operation is regarded as simply ridiculous. Ben Mohsen is one of a handful of Iranians who live in Corpus Christi. They all seem to know each other, help each other with their upbringing a common touchstone. When he first heard that 'Jack' was involved in such an elaborate plot, he thought someone had stolen his identity: "He's incompetent. He wasn't capable of doing such a thing, not even near what he's accused of. How he got mixed up in this - we are all shocked - we don't know".

When asked if he was the sort of man who could co-ordinate an international operation which would involve money from Iran, hitmen from Mexico and a target in Washington DC, Ben looks almost exasperated: "Somebody needs to take care of Jack, he's just like a baby. I don't know how many cell phones he's lost. He couldn't do anything himself. He would put socks on the wrong feet, they would be different colours. That's the kind of person he was."

Taking time to dig out more information about Arbabsiar reveals that he was on the edge of the city's drug culture. "He knew users but I never saw him use himself," one man tells me. He was not religious or political. "Politics? He couldn't spell the word," says another acquaintance.  He visited prostitutes and had a number of minor criminal convictions mainly for motoring offences.  

The prosecution suggests that while on a visit home to Iran, he met a cousin who was a senior figure in the Republican Guard. This would be the relative Arbabsiar boasted was a general who worked undercover but also apparently was interviewed on an international news channel. He suggested he use his contacts in the US to reach out to a Mexican Drug cartel to carry out an operation to assassinate the Saudi ambassador to the United States.

Many analysts reject the idea that the highly professional Republican Guard, which has been linked to political assassinations in the past would entrust such a risky and sensitive operation to a failed second-hand car salesman and an organisation thought to be riddled with informers rather than farm out the contract to trusted proxies used in the past or even use a professional operator. And journalists in Mexico wonder why an organisation which makes billions in drugs profits and extortion would even think about carrying out an operation which would attract the wrath of the authorities on both sides of the border for $1.5 million.

Yet it's alleged that on his return to the US, Arbabsiar tried to make contact with someone he believed knew senior figures in the cartel, but was actually an American government informer.

Jimmy Evans used to travel to car auctions with 'Jack' but never saw any suggestion he had links to 'dangerous' people: "He might have partied and did what he wanted to do, but when you start messing with people down there," he says pointing towards Mexico, "you are messing with people you shouldn't be messing with".

In the official Federal complaint, it is revealed that the suggestion to target the Saudi Ambassador came from the mysterious government informant, not Arbabsiar. John Perry who acted as Jack's lawyer in minor cases in the past says there was "nothing to suggest, nothing to indicate to me he would have that sort of personality or capability, that he could escalate things to that sort of level".

The FBI says Arbabsiar has made a full confession to the role he played in the international plot, even though he is likely to plead not guilty when the case comes to court. US government officials say the plot - which has serious implications and consequences for Iran - reads like a plot from a movie. But in Texas, some believe Mansoor Arbabsiar is an unlikely villain.