CREATE TABLE table_23465 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "U.S. viewers  ( millions ) " TEXT)

What's the series number of the episode titled 'Rapture'?
SELECT "No. in series" FROM table_23465 WHERE "Title" = 'Rapture'
SELECT "No. in series" FROM "table_23465" WHERE "Title" = 'Rapture'