Dr. Wells' former protégée, Hartley Rathaway, returns to seek revenge on his mentor after being affected by the particle accelerator explosion. Now able to manipulate sound waves, the brilliant Rathaway is a dangerous threat to both Wells and The Flash. Meanwhile, Iris is thrilled when she's hired by the Central City Picture News as their newest cub reporter. Unfortunately, her editor pairs her with a veteran reporter, Mason Bridge, who wants nothing to do with her. Cisco recalls his first day on the job at S.T.A.R. Labs when he met Hartley and Caitlin. Joe asks Eddie for a favor but asks him to keep it a secret from Barry.