Who are the cast members of episode 3-04?
CREATE TABLE "series_3_spearhead_in_hong_kong" (
  "episode_num" text,
  "original_air_date_uk" text,
  "episode_title" text,
  "director" text,
  "writer" text,
  "cast" text
);
SELECT "cast" FROM "series_3_spearhead_in_hong_kong" WHERE "episode_num"='3-04';