CREATE TABLE table_1309 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "U.S. viewers  ( millions ) " TEXT)

Who was the writer when there were 15.85 million US viewers?
SELECT "Written by" FROM table_1309 WHERE "U.S. viewers (millions)" = '15.85'
SELECT "Written by" FROM "table_1309" WHERE "U.S. viewers (millions)" = '15.85'