Dr. Wells' former protégé, Hartley Rathaway, returns to seek revenge on his mentor. Meanwhile, Iris is hired as a cub reporter; Cisco recalls his first day on the job at S.T.A.R. Labs; and Joe asks Eddie for a favor but asks him to keep it a secret from Barry.
Quest roles:
Andy Mientus(Hartley Rathaway / Pied Piper), Morena Baccarin(Gideon (voice) (uncredited)), Roger Howarth(Mason Bridge), Tom Butler(Eric Larkin), Sarwan Badesha(Cop), Quynh Mi(Woman)