The mass-murder trial of two Libyans charged with the 1988 mid-air bombing of a Pan Am jumbo jet may unlock secrets that could block the path of improving Western relations with old adversaries in the Middle East.
If the two are found guilty of blowing up Flight 103 over Lockerbie in Scotland, reconciliation between the Libyan leader, Col Muammar Gadafy, and Western powers whose oil companies want to do business with him could be slowed dramatically.
If they are acquitted, the West will want to know who really ordered and who carried out the attack which killed 270 people, most of them Americans and Britons.
Signs before the opening of the trial yesterday indicated it may lead back to old suspects.
Defence lawyers for the Libyans hint they will try to prove Syrian-backed Palestinian extremists were the perpetrators, in an act of revenge on behalf of Iran for the destruction of an Iranian airliner by a US naval ship six months earlier.
Iran vowed the skies would "rain blood" after the USS Vincennes shot down an Iran Air flight in July 1988, killing 290. It was widely assumed at first that Tehran ordered the destruction of the Pan Am airliner, with Syrian-sponsored help.
Shifting suspicion for one of the most shocking acts of modern terrorism back on to Damascus or Tehran could deal a serious blow to their improving relations with the West.
Some commentators suggest suspicions about Syria's role were dropped when the West needed its support for the 1990 Gulf War.
The Lockerbie defence can be expected to plunge into these murky waters, drowning the case against their clients in a morass of contradictory but plausible circumstantial evidence and testimony that points elsewhere.
The Frankfurt-London-New York flight, a Boeing 747, exploded at 31,000 feet on the evening of December 21st, 1988.
Prosecutors aim to prove that the Libyans placed a Toshiba radio-cassette recorder full of Semtex explosive in a suitcase and smuggled it aboard a plane from Malta to Frankfurt, where it was checked through on to the doomed Pan Am flight.
The prosecution must prove that the suitcase bomb began its fatal journey from Malta's Luqa Airport where the accused managed operations and security for Libya's national airline.
Prosecutors contend they were secret agents whose action was intended to "further the purposes" of the Libyan intelligence service. In 1986 Libya was bombed by US planes flying from Britain on a punitive strike that killed Col Gadafy's daughter.
The prosecution maintains that a fingernail-size fragment of electronics board found in a Scottish forest came from a timing device of a type sold exclusively to Libya by its Swiss manufacturer, Mebo, and tested in the Libyan desert.
But a Libyan defector and star prosecution witness who allegedly saw the suitcase being placed by one of the men on to a loading conveyor is said to have changed his story, saying what he actually saw was the case being removed.
A Swiss witness who made the timer reportedly insists the fragment comes from a prototype sold to the East German state security service, believed to have passed it on to the Popular Front for the Liberation of Palestine-General Command (PFLP-GC).
German police arrested over a dozen PFLP-GC members operating in Frankfurt just two months before the Pan Am explosion and seized a Toshiba cassette bomb of the type which could have been taken aboard the jumbo at Frankfurt.
A British Channel Four television documentary in the mid-1990s said Palestinian terrorists had infiltrated a US intelligence operation which used Pan Am Flight 103 to smuggle heroin, in a complex dirty-tricks, drugs-for-hostages deal.
Eight US intelligence officers from two agencies were aboard the doomed flight and died over Lockerbie. An alleged Palestinian "drug mule", Khaled Jaafar, was also a victim.
The Palestine Liberation Organisation, however, is said to have concluded that the bomb was commissioned by Iran and carried by the PFLP-GC, and made its way from Beirut to Belgrade and on to Frankfurt Airport via tourist coach.
Lockerbie prosecutors intend to show that a tweed jacket and an umbrella found in the plane wreckage were bought in a shop in Malta to stuff the brown bomb suitcase, and that the shop owner identified one of the Libyans as the purchaser.
But Malta denies an unaccompanied bag ever left Luqa Airport and has won a libel action in London on the charge.
The Lockerbie defence team is reported to be planning to try to incriminate Mohammed Abu Talb, a Lebanese PFLP-GC member jailed in Sweden for terrorism, whose kitchen calendar had the date of the Lockerbie bombing circled when his home was raided.
Talb, convicted in 1989 of blowing up US airline offices in Scandinavia, was one of the first suspects to be identified in the Lockerbie case, but was never arrested. His true role, if any, will remain an enigma until defence lawyers introduce their case.
One thing all appear to agree on is that the two Libyan accused, Abdel Basset al-Megrahi and Al-Amin Khalifa Fahima, were not freelance bombers who hatched the conspiracy alone but low-level apparatchiks, or even innocent scapegoats.