Table: tv_episode_viewers_2
Columns: no_in_series
no_in_season
title
directed_by
written_by
original_air_date
u_s_viewers_millions

Question: How many U.S. viewers watched the episode directed by Frank Waldeck?
SQL: SELECT "u_s_viewers_millions" FROM tv_episode_viewers_2 WHERE "directed_by" = 'Frank Waldeck'