What favorite American comedy takes as its themes mental illness, elder abuse and serial murder? Why, “Arsenic and Old Lace,“ the 1941 Joseph Kesselring chestnut about two old ladies with a body in the window seat. This is the reliable farce about elderly sisters living in their family’s longtime Brooklyn home who like to dispatch lonely old men by serving them poisoned elderberry wine. They have three nephews: Mortimer, the drama critic for a New York newspaper; Teddy, who thinks he’s Teddy Roosevelt; and Jonathan, who has been away for a few decades but is back after a stint in an institution for the criminally insane.