He is at the center of a growing storm in Bahrain, his name is invoked with reverence by anti-government protesters, and yet his whereabouts remains a mystery. This much is known: Sheik Abdul Amir al-Jamri, 59, the Islamic leader of an opposition movement that is roiling this Persian Gulf sheikdom, was last arrested in January 1996. Not even his lawyers are certain where the bearded Shi'ite cleric is currently imprisoned. They believe he is in Qulaa, the fortlike police headquarters in Manama, the island nation's capital, but released inmates claim to have sighted him at a military camp in the town of Safra in central Bahrain. Though he has been held incommunicado throughout the past six of the 19 months of rioting and sporadic violence, al-Jamri is accused of complicity in the unrest. He was originally arrested for political agitation, but last month government officials suggested that he might be part of an Iranian plot, using radical Shi'ites from Bahrain to overthrow Emir Isa bin Salman al-Khalifa, whose family has controlled the island nation since the 18th century.

The turmoil, which raises concerns about the 3,000 U.S. sailors and their families in Bahrain, stems from the growing conflict between the relatively poor Shi'ites, two-thirds of the 363,000 Bahraini population, and the Khalifa, whose monarchy is anchored by support from the more affluent minority Sunnis. If the government does decide to try al-Jamri--Bahrain's ranking Shi'ite leader--for sedition, as officials hint is likely, the violence is certain to get worse. The Shi'ites began a campaign of street clashes and bombings in 1994, underlining their angry demands for political rights and better social conditions. The government responded with a crackdown that has failed to end the disturbances. As a Western diplomat in Manama says, "No doubt, the government has a tiger by the tail."

For years, Bahrain's openness to foreign businessmen and legalization of alcohol made it a symbol of tolerance among the gulf's conservative monarchies. Now it has become a microcosm of the region's worst nightmare--a society doubly plagued by declining oil wealth and rising Islamic fundamentalism.

By reputation, al-Jamri is a moderate with nothing in his past to mark him as a likely proponent of terrorism. He studied theology in the Iraqi city of an-Najaf, the seat of Shi'ite Islam, for 11 years, but he returned to Bahrain in 1973. He was then elected to the nation's new parliament, which the Emir suspended after just two years when the Khalifa clan began to feel threatened by its demand for more authority. By 1988 al-Jamri's calls for reform led to his suspension after 11 years as an Islamic court judge. Allied with some Sunnis and even a handful of secular liberals, he petitioned for the restoration of parliament. Eventually the regime arrested him.

Meanwhile, Shi'ite militants began a wave of violent attacks on policemen, power stations and even schools. In mid-1995 al-Jamri was released from prison on condition that he cease agitation, help calm tensions and work toward a political compromise. When the deal collapsed, Shi'ite militants launched a bombing campaign, provoking a crackdown and the rearrest of al-Jamri. In a recent report, Amnesty International criticized government measures, alleging that security forces have arrested and beaten women, including one of al-Jamri's daughters.

A month ago, the government unveiled what it claimed was an Iranian plot to oust the Khalifa. "There was a plan supported by Iran to overthrow the regime," Foreign Minister Sheik Mohammed bin Mubarak al-Khalifa told TIME. "[Al-Jamri's] movement, which says, 'We want democracy,' really wants an Iranian-style [state]." Al-Jamri has not been formally charged, but one of the alleged Bahraini plotters was put on television, confessing that the sheik had given his blessing to the bombings.

Al-Jamri's lawyers and family acknowledge his religious links with Iran but deny he was involved in any plot. Foreign diplomats say that while intelligence information confirms Iranian recruitment and training of Bahraini Shi'ites, it cannot corroborate claims linking al-Jamri himself to the plot.

The Khalifa regime's determination to crush the Shi'ite rebellion is making many Bahrainis nervous. "The trial could pave the way for more radical groups to come to the surface," says al-Jamri's exiled son Mansour, 35, an activist and engineer working in Britain. "We are moderates, but some people will feel the time has come to speak the language that the government will understand."

A sensible dialogue could still forestall more violence, but both sides must retreat from the escalating intolerance depicted in a colorful graffiti war being waged across the country. In the village of Diraz, antigovernment activists spray-painted WE WANT AL-JAMRI!, then stenciled a red portrait of the Islamic leader. The next day a policeman crossed out the slogan, drew a pair of satanic horns on the portrait and scrawled TO HELL WITH AL-JAMRI! The next day the activists were back with a more menacing message: DEATH TO THE KHALIFA!