Marseille, France // Cherchez la femme. The old cliche has it that in most detective stories, and often enough in real-life murder mysteries, you look first for the woman at the heart of the case.
And when it comes to western intervention in overseas conflict, so the cynical view goes, it becomes a matter of cherchez l'argent, or look for the money - identify the economic interest the West sees in events going in a particular way.
Such a notion naturally overlooks, in the case of Libya, the broad international consensus that Col Muammar Qaddafi was treating his people abominably. There were fears of wholesale massacre in Benghazi and elsewhere as the unpredictable old dictator fought back against the rebels.
But despite high-minded justifications for action it took no time for suspicions to surface.
In Italy, Libya's colonial ruler for more than 30 years, the head of the Senate's defence affairs committee, Gianpiero Cantoni, said French attempts to keep its leading role in the UN-backed action rather than transfer command to Nato were driven by hopes of future oil contracts with a new Libyan government.
France was hardly alone among coalition partners in having been willing in recent years to deal with the old-look regime. But Paris undoubtedly made a meal of Col Qaddafi's transition from international pariah to acceptable head of state. Few have forgotten the lavish welcome afforded by the president, Nicolas Sarkozy, when his Libyan counterpart visited France in 2007.
The picture tell its own story, with Col Qaddafi's left arm raised in apparent triumph during handshakes on the steps of the Elysee. Mr Sarkozy had reason to be pleased, too. Deals worth €10 billion (Dh53.76bn) for Airbus jets and nuclear power co-operation were signed during the visit.
On March 21 this year, the president greeted world leaders at the same palace to decide how to implement action many saw as intended to hasten Col Qaddafi's downfall. But has the conflict benefited France or its president as he faces a tricky fight for re-election next spring?
In some ways, the signs could hardly seem worse. Drivers have been left fuming at the pumps in France as elsewhere. Cuts in Libyan output have sent fuel prices soaring. Prices heading towards €2 a litre are the last thing an already unpopular president needs.
When Christophe de Margerie, the chief executive of Total, which has extensive oil interests in Libya, predicted recently that figure would be reached Mr Sarkozy rushed to slap him down. French people are now learning that hundreds of shipyard workers may be laid off in the western port of Saint-Nazaire as payment is blocked by UN sanctions on a cruise ship ordered by GNMTC, a Libyan state company that has Col Qaddafi's son Hannibal as first management consultant.
The Libyan crisis also has serious financial percussions for other countries. Stefan Karisson, an economist based in Sweden, estimated in his Christian Science Monitor blog that the US government's engagement in the conflict had cost it more than Dh2.2bn.
Mr Karisson said the sharply rising cost of oil imports was also causing pain for the US and other coalition members such as France and Britain. And Italy has a nervous eye on its extensive economic interests in Libya.The France Soir newspaper calculates that for France alone, the cost of military involvement in Libya approaches Dh8 million a day before taking into account the weapons fired.
It is clear that whatever divides them on detail, all of the coalition powers need a breakthrough. War and its knock-on effects can be an expensive business and the French defence minister, Gerard Longuet, has warned this one could be a drawn-out affair.
Perhaps when Mr Sarkozy and the Italian prime minister Silvio Berlusconi meet in Rome next week they will find more of common interest to talk about than their differences on how to cope with the exodus of Tunisian refugees.