AS plots go it's been called "an amateur hour scheme" or something that resembles a "rejected Quentin Tarantino script".

I’m talking about the alleged attempt by Iranian agents, with the help of Mexican drug cartel hitmen, to kill Saudi Arabia’s ambassador to Washington, Adel al Jubeir, on American soil.

The US authorities’ account of how they foiled the plot has – from Tijuana to Tehran – simultaneously fascinated and bemused intelligence analysts, diplomats, law enforcement officers and the general public alike.

Some well-placed people in the US have even gone as far as to openly voice their scepticism about certain aspects of the affair. Among the latest is Kenneth Katzman, a senior Middle East analyst at the Congressional Research Service in Washington, and scholar Gary Sick at Columbia University’s Middle East Institute, who once monitored Iran for the US National Security Council.

Most of their doubts arise from some very pressing questions. To begin with, even if the allegations are true, what would the Iranians have to gain from such a plan? And, if Tehran had little to gain, who might?

Then there is the question of the timing, not only of the alleged plot, but the decision by the US Government to release details and the indictment against the two Iranian suspects Manssor Arbabsiar and Gholam Shakuri.

Is it perhaps the case that this whole affair provides clues to wider events just beginning to unfold in the Middle East?

Before weighing this up, though, let’s stop to consider the claims of Mexican drug cartel involvement.

According to the details of the charges Manssor Arbabsiar faces, he is said to have approached an individual, already on the payroll of the US Drug Enforcement Administration (DEA), who he thought had links to a “large, sophisticated, and violent drug-trafficking cartel”.

Some sources say that cartel was the infamous Los Zetas.

Taken at face value, it’s certainly the case that Los Zetas – or its competitor cartel, the Sinaloa Federation – has the wherewithal to co-operate with international operatives embarking on terrorist campaigns. In this instance, however, the cartels had much more to lose than gain.

Already tied up with their own turf wars, they are primarily criminal business organisations who let little get in the way of generating their vast illegal profits – sums that make what Arbabsiar was offering his hitman organiser look like lunch money by comparison.

What’s more, Los Zetas – like other cartels – has, in the past, had no hesitation in hunting down and killing those individuals who jeopardise its narcotics networks through high-profile political acts that could further invoke the wrath of the US and Mexican security services.

While US Attorney General Eric Holder insisted the Iranian suspects were “directed and approved by elements of the Iranian Government”, Washington has yet to make the direct link between the plot and either President Mahmoud Ahmadinejad or Supreme Leader Ali Khamenei.

There is, however, always the possibility that the assassination attempt on Adel al Jubeir was carried out by rogue elements of the Islamic Revolutionary Guard Corps – a covert-action unit which was informally known as Birun Marzi, “Outside the Borders”, but today goes by the name the Quds Force.

Cadres doubtless exist within Quds Force’s ranks who would happily stir things up with the Americans and Saudis.

But for the Iranian Government itself to have officially sanctioned such an assassination attempt would effectively have constituted a declaration of war against the US, something Tehran is unlikely to initiate given that it lives increasingly in fear of military attack by Washington’s ally, Israel, over its nuclear programme.

Would Iran really risk all-out war with both powers through an amateurish, ill-conceived murder-for-hire plot, killing two ambassadors and an unknown number of American citizens?

Likewise, too, there are holes in the theory emanating from some US quarters that Iran’s ongoing cold war with rival Saudia Arabia in the wake of the Arab Spring might have given rise to the plot.

Surely, if Iran really wanted to go head-to-head with Saudi Arabia, it would more likely do so over Saudi’s intervention in Bahrain which, like Iran, has a predominately Shia Muslim population.

As befitting such a shadowy, labyrinthine tale, observers have rightly flagged up that, given the state of relations between the US and Iran, it might also be in the interests of others to stir up trouble between the two countries. There has been considerable alarm in Washington, London and elsewhere over reports that intense discussions have been underway within Israeli military and security circles about whether or not to launch a military strike against Iran’s nuclear facilities.

According to Middle East specialist Patrick Seale, the key issue concerning the Israelis was how to “ensure the United States took part in the attack or, at the very least, intervened on Israel’s side if the initial strike triggered a wider war”.

The pressure, says Mr Seale, is now on, with some Western military experts having been quoted as saying the window of opportunity for an Israeli air attack on Iran will close within two months, as the onset of winter would make such an assault more difficult.

It seems Israeli concerns centre not only on how close Iran is to acquiring the capability to manufacture a nuclear bomb, but that the five permanent members of the Security Council plus Germany may accept an Iranian offer of renewed talks.

While it’s doubtful the US, which is still struggling to fully extricate itself from Iraq and Afghanistan, would have any desire to engage in all-out conflict with Iran, there have been suggestions that, should the bomb plot against the Saudi ambassador have been successful and killed American citizens, it would in principle have given the US reason for taking military action against Mr Ahmadinejad’s regime.

So far there remains more questions than answers over this affair. The plot, as they say, thickens.