Dr. Wells' (Tom Cavanagh) former protegee, Hartley Rathaway (guest star Andrew Mientus), 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 (Grant Gustin). Meanwhile, Iris (Candice Patton) is thrilled when she's hired by the Central City Picture News as their newest cub reporter. Unfortunately, her editor (guest star Tom Butler) pairs her with a veteran reporter, Mason Bridge (guest star Roger Howarth), who wants nothing to do with her. Cisco (Carlos Valdes) recalls his first day on the job at S.T.A.R. Labs when he met Hartley and Caitlin (Danielle Panabaker). Joe (Jesse L. Martin) asks Eddie (Rick Cosnett) for a favor but asks him to keep it a secret from Barry.
