COLUMBUS, OH—With the Sunday afternoon departure of friends visiting from Chicago for the weekend, the apartment of Gary and Felicia Mylan ceased being a warm, open household and returned to its normal atmosphere of icy resentment. "They're gone," said Felicia Mylan, dropping the relaxed demeanor she had affected for three days and clenching her teeth as her husband opened his laptop to read e-mail and shut off any possibility of conversation. "I'm going to lie down for a bit." The weekend marked the lowest level of tension in the home since February, when the couple shared a chuckle over news of an acquaintance's three-month-old marriage ending in divorce.