One of the saddest times Joelle van Dyne ever feels anywhere is that invisible pivot where a party ends — even a bad party — that moment of unspoken accord when everyone starts collecting his lighter and date, jacket or greatcoat, his one last beer hanging from the plastic rind’s five rings, says certain perfunctory things to the hostess in a way that acknowledges their perfunctoriness without seeming insincere, and leaves, usually shutting the door.