Twin Cities nurses and hospitals turned their bitter labor standoff into a surprise settlement Thursday, concluding a suspense-filled day of secret talks and averting the biggest nursing strike in U.S. history. The 3 p.m. announcement stunned many members of the Minnesota Nurses Association, who had been bracing for a strike Tuesday. Instead of striking, they'll be voting on the agreement that day. At 1 a.m. Wednesday, the two sides had grimly broken off negotiations and announced that there was "no reason to talk." But by 11 p.m., they had quietly returned to the bargaining table and hammered out a tentative agreement, which was formally endorsed by the union leadership Thursday.