Guest host Josh Radnor presents two stories about marriage and its challenges. In Helen Phillips’ “The Knowers,” a wife wants the answer to an ultimate question, but her husband does not. It’s performed by Stockard Channing. The “Three Little Maids” of Alix Ohlin’s story are a middle-aged man’s ex-wife, current wife, and daughter. The story is performed by Mia Dillon.