We do not know what happened in Syria on September 6.  Those few who do know — officials of Israel, Syria and possibly North Korea and/or Iran — aren't saying.  The story is, as one headline put it, "shrouded in mystery."

What is known is that an Israeli air strike inside Syria "left a big hole in the desert," unnamed sources told CNN.  In fact, the broad and intentional silence makes the incident all the more important.  As the Washington Post put it in an editorial this week, "like a subterranean explosion, the event is sending shock waves through the Middle East and beyond." 

Here's Bret Stephens, a former editor of the Jerusalem Post, now at the Wall Street Journal:  "What's beyond question is that something big went down on Sept. 6.  Israeli sources had been telling me for months that their air force was intensively war-gaming attack scenarios against Syria; I assumed this in anticipation of a second round of fighting with Hezbollah.  On the morning of the raid, Israeli combat brigades in the northern Golan Heights went on high alert, reinforced by elite Maglan commando units.  Most telling has been Israel's blanket censorship of the story — unprecedented in the experience of even the most veteran Israeli reporters — which has also been extended to its ordinarily hypertalkative politicians.  In a country of open secrets, this is, for once, a closed one."

Regardless of the silence, there are at least four separate speculations among the generally informed, none of which is conducive to good sleep for world leaders or citizens.

The first speculation, that Israel attacked some type of nuclear facility or nuclear supplies being transferred to Syria from North Korea, raises the scariest implications. 

Here's the Washington Post again:  "The Post's Glenn Kessler reported that the strike came three days after a ship carrying material from North Korea docked at a Syrian port and delivered containers that Israel believes held nuclear materials.  It's not clear whether U.S. intelligence agencies concur with Israel's conclusion, and independent experts have said that Syria lacks the resources for a credible nuclear weapons program."

"Another proposition," writes Peter Brookes in the New York Post, "is that North Korea is trying to stash its nuclear stuff in Syria before it has to come clean as part of denuclearization talks now under way with its neighbors and the United States.  That might explain why Damascus has been mum on the Israeli strike:  The loss was North Korea's, not Syria's."

The second speculation arises from an unrelated report in Jane's Defence Weekly, regarding an accidental explosion at a Syrian chemical weapons base last July where both Syrian troops and Iranian weapons engineers were killed.  According to the authoritative British publication, the Syrians were attempting to fit a Scud missile with a mustard-gas warhead.

While targeting Syrian chemical weapons facilities would be in Israel's interest, probably not urgently enough to mount the first air attack on the country since 2003.

The third speculation is, from reporting by Mark Mazzetti and Helene Cooper of the New York Times based on interviews with Washington officials, "that the most likely targets of the raid were weapons caches that Israel's government believes Iran has been sending the Lebanese militant group Hezbollah through Syria.  Iran and Syria are Hezbollah's primary benefactors, and American intelligence officials say a steady flow of munitions from Iran runs through Syria and into Lebanon."  Christiane Amanpour of CNN has reported the same explanation.

The fourth speculation is that the raid was a "dry run for attack on Iran," ventured by British journalist Peter Beaumont of the Observer.  Of all, that seems the least likely explanation for such an aggressive air strike.

As Bret Stephens of the Wall Street Journal puts it, "Could we have just lived through a partial reprise of the 1981 Israeli attack on Iraq's Osirak nuclear reactor?  On current evidence, it is the least unlikely possibility."  That is about as definitive as journalists have been able to get.

On September 20, President Bush at his news conference refused to make any comment at all regarding the incident, although he was pressed several times.  That silence, along with a similar response from Israeli Prime Minister Ehud Olmert and the muted reaction from Syria, is not a good sign.

We dislike speculation as much as we dislike alarmism.  Unfortunately, those are the only components this disquieting story has for the moment.