S6, E4: While attending a fundraiser, Lois witnesses the Green Arrow (recurring guest star JUSTIN HARTLEY) snatching a rare diamond necklace off of Martha's neck and vows to find out about the man behind the costume. Clark does some investigating of his own and discovers that the Green Arrow is actually Oliver Queen, who has been stealing from the rich and giving to the poor. Meanwhile, Lex enlists Lionel's help in testing Lana's loyalty.