CREATE TABLE table_3682 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "U.S. viewers  ( million ) " TEXT)

Which episode number had a viewership of 0.56 million?
SELECT MAX("No. in series") FROM table_3682 WHERE "U.S. viewers (million)" = '0.56'
SELECT MAX("No. in series") FROM "table_3682" WHERE "U.S. viewers (million)" = '0.56'