Former Sen. George Mitchell, who worked magic in helping broker a plan for peace in Northern Ireland last year, has been called for a return engagement, this time to review what has gone wrong in the stalled process that many hoped would bring to decades of bloody conflict between Protestants and Catholics in the British-controlled province.

The peace agreement, signed by all factions on Good Friday 1998, came after two years of negotiation and Sen. Mitchell’s daily involvement. Sen. Mitchell now will focus on the two issues that threaten to derail the plan: the creation of an executive branch of government that will guarantee the inclusion of Sinn Fein, the principal Catholic party that advocates a unified Republic of Ireland; and the decommissioning of paramilitary weapons by May 2000.

Sen. Mitchell has a weapons problem — he must convince Gerry Adams, leader of Sinn Fein, that an agreement on a timetable for decommissioning the IRA’s weapons must occur now. Better yet, a voluntary decommissioning of a small percentage of the weapons would force David Trimble, leader of the dominant Protestant party, the Ulster Unionists, to return to the process of appointing a cabinet, including members of Sinn Fein, at the Northern Ireland Assembly.

Politcal fights aren’t simple anywhere, but they are particularly complicated in Northern Ireland. The backdrop in this case is that the somewhat moderate Mr. Trimble apparently was afraid that some of his party members were ready to vote for Ian Paisley, the reactionary leader of the pro-Protestant Democratic Unionist Party. The IRA, on its side, has any number of theories on how decommissioning before being seated in the cabinet is an attempt to destroy it.

Perhaps Mitchell’s greatest accomplishment has been Sinn Fein’s acceptance of the principle of consent, that the majority of the people of Northern Ireland will decide if and when they will reunite with Ireland. Right now, a clear majority are in favor of remaining aligned with England. Sen. Mitchell also succeeded in persuading Mr. Trimble that peace required that Sinn Fein be allowed to hold cabinet offices, a position he now appears to be regretting.

Sen. Mitchell’s underlying task is to convert Mr. Adams and Mr. Trimble from political animals to national statesmen. Such a conversion will be nothing short of miraculous.