CREATE TABLE "table1_22078906_2" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_airdate" text,
  "u_s_viewers_millions" text
);

Question: What number episode in the series was watched by 15.89 million U.S. viewers? 
SQL: SELECT "no_in_series" FROM "table1_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 "table1_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 "table1_22078906_2" WHERE "title"='\"Once a Hero\"';

Question: Who wrote the episode titled "In the Dark"?
SQL: SELECT "written_by" FROM "table1_22078906_2" WHERE "title"='\"In the Dark\"';