If you're not confused - you don't understand it, experts in the Northern Ireland conflict have often said. Like previous crises, the latest impasse is complex. John Downing untangles the key issues.
Q. What sparked this latest crisis?
A. Two senior republicans were murdered this summer in Belfast. In late August, senior PSNI officers said they were investigating potential involvement by Provisional IRA members. DUP leader and First Minister Peter Robinson said, if this was proven, Sinn Féin would face expulsion from the power-sharing executive. Gerry Adams and other Sinn Féin leaders adamantly insisted the "IRA left the stage in 2005". PSNI Chief Constable George Hamilton said the IRA still existed but "not on a war-footing". In the Republic a fresh assessment of the IRA was ordered.
Q. Is internal unionist rivalry a factor?
A. Yes. The smaller Ulster Unionist Party, supplanted over the years by the late Ian Paisley's DUP, upped the ante by quitting the executive. Mr Robinson is also expected to retire, creating leadership jockeying. That has not helped. But the real and recurring problem is unionists' fear that Sinn Féin at least turns a blind eye to republican criminal activity. That suspicion is shared by Fine Gael, Fianna Fáil and Labour in the South. Sinn Féin insist they are victims of political jealousy.
Q. What drove things to the brink?
A. Several key republicans, including Sinn Féin Northern chairman Bobby Storey, were arrested for questioning. Mr Storey, a good friend of Mr Adams, has since been released and says he'll sue the PSNI. The DUP failed in efforts to adjourn the North's assembly. Then the DUP quit the executive - leaving just one minister in a caretaker capacity. The entire power-sharing apparatus, created by the 1998 Good Friday Agreement, is yet again on the brink of total collapse.
Q. What happens now?
The London and Dublin governments are trying to put the Belfast political humpty dumpty back together again. All-party talks are expected next week. Sinn Féin insist they are staying with it. These North institutions have worked poorly or not at all. But a long-term absence could leave a dangerous vacuum.