Question: What number episode in the series was watched by 15.89 million U.S. viewers? 
SQL: SELECT "No. in series" FROM "1-22078906-2" WHERE "U.S. viewers (millions)" = '15.89';

Question: What is the title of the episode directed by William Webb? 
SQL: SELECT "Title" FROM "1-22078906-2" WHERE "Directed by" = 'William Webb';

Question: How many millions of U.S. viewers watched the episode titled "Once a Hero"?
SQL: SELECT "U.S. viewers (millions)" FROM "1-22078906-2" WHERE "Title" = '"Once a Hero"';

Question: Who wrote the episode titled "In the Dark"?
SQL: SELECT "Written by" FROM "1-22078906-2" WHERE "Title" = '"In the Dark"';