Who was the 3rd performer when christopher smith was the 2nd performer?
CREATE TABLE "series_4" (
  "date" text,
  "episode" real,
  "performer_1" text,
  "performer_2" text,
  "performer_3" text,
  "performer_4" text
);
SELECT "performer_3" FROM "series_4" WHERE "performer_2"='christopher smith';