CB: A former employee of S.T.A.R. Labs comes after Wells for revenge, using sonic technology as a weapon. While Barry fights the menace, his companions at S.T.A.R. Labs face their past so that they can help. Meanwhile, Iris faces a new challenge in her life and Joe and Eddie start a new investigation. As for Harrison Wells, he is a man of many secrets. How long can he keep them all from the people closest to him?