Like the dog that did not bark in the old mystery tale, a distinctly unassertive Syrian ''observer'' has dominated a gloomy weekend at the Lebanon reconciliation conference.
Left largely to themselves, the rival Lebanese Christian and Muslim negotiators had failed in six days of talks by Sunday evening to resolve the issues their militiamen have been fighting over for nine years - principally the way political power should be shared among Lebanon's various communities.
Back in Lebanon, rival gunmen took the occasion to begin whittling away at a cease-fire imposed by the Syrians here earlier in the week. Thankfully, there was still nothing like the full-scale war of February. Yet in the bleak tradition of past Lebanese ''truces,'' eight people were killed and three times that many injured in a single 24-hour period Friday and Saturday.
A junior United States diplomat was also kidnapped in Beirut Friday. American efforts in contacts here with both Lebanese government and factional leaders had , by late Sunday, provided no clue to the envoy's fate.
Still, sources from various of the rival Lebanese camps here were continuing to assume Sunday evening, that Syria's delegate - Vice-President Abdel Halim Khaddam - would step in at some point to impose compromise on the increasingly hot-tempered Lebanese negotiators.
A Syrian journalist put it directly: for the conference to succeed, Mr. Khaddam will at some point have to ''reach into his pocket'' for a draft compromise for Lebanon's political future.
Why Mr. Khaddam had not yet done something along those lines was unclear. One theory was that he wanted to wait until the rival Lebanese had agreed on what little they, alone, could manage and then dramatically emphasize Syria's key role by imposing a compromise.
The gloom produced this weekend by the wordslinging here and the gunslinging back in Lebanon has encouraged doubts as to how substantive or lasting even a Syrian-imposed solution might prove.
That the conference would end with some publicly announced accord was still taken Sunday as virtually certain. Mr. Khaddam, at least, was reported to have made clear to the Lebanese that he was determined to stay in lakeside Lausanne every bit as long as necessary to get the Lebanese to agree among themselves.
But two very different kinds of accords seemed possible. One would be a genuine compromise on root issues of Lebanon's political future. Another, to borrow a preferred phrase from Lebanese Druze militia chief Walid Jumblatt, would be a mere ''piece of paper'' - vague enough for the feuding groups to accept, yet too vague to get at the issues for which they have been killing each other.
No accord of either type had been announced by Sunday afternoon.
Sources supportive of the two main non-Christian militia leaders at the Lausanne conference - Jumblatt and Shiite Muslim chief Nabih Berri - went so far as to report Sunday that their bosses were running out of patience, had almost packed for home Saturday night, and were directing the gunmen back home to get prepared for the possibility of resumed, large-scale fighting with Christian fighters. But in conversation with friends over the weekend, the leaders themselves denied plans to stage a walkout.
Syrian envoy Khaddam, meanwhile, continued late Sunday to sit in on informal meetings among various Lebanese rivals attending the conference.
Though by no means mute in such encounters before, he is said to have done more listening than talking. The fate of this conference will become clearer only when that equation is reversed.
''Neither victors nor vanquished,'' said one Syrian privately, describing his country's position on the Lebanese imbroglio.