This weekend, the war on terrorism is a war of nerves. It’s a weekend for sealing windows with plastic and duct tape, for wondering whether the briefcase across the aisle holds a bomb, for sitting down with the family to plan for the unplannable. It’s a weekend when some Americans will relax by the pool or go ice fishing, while others will ready their home safe rooms, install a wood stove or stock up on ready-to-eat meals. It’s a weekend when police will look for men with facial nicks that might indicate a freshly shaved Islamic beard. A confluence of potential plagues — war abroad, terrorism at home, schism among allies — has a nation that thought it was recovering from the Sept. 11 terrorist attacks on edge once again. Full Story