Here’s the official synopsis for episode 17 of ‘The Flash’ Season 2, titled “Flash Back.”
“Flash Back” — (8:00-9:00 p.m. ET) (TV-14, LV) (HDTV)
A MOMENT IN TIME GETS BARRY ONE STEP CLOSER TO ZOOM; ANDY MIENTUS RETURNS AS HARTLEY RATHAWAY – After the shocking revelation that Zoom is Jay Garrick (Teddy Sears), Barry (Grant Gustin) is more determined than ever to get back to Earth-2 to stop Zoom forever. Desperate to find a way to increase his speed, Barry decides to travel back in time and masquerade as his earlier self in order to get his arch-nemesis, Dr. Harrison Wells/Eobard Thawne (Tom Cavanagh), to teach him how to run faster. However, things don’t go as planned and Barry is stunned to face familiar foe Hartley Rathaway (guest star Andy Mientus), as well as old friend Eddie Thawne (guest star Rick Cosnett). Iris (Candice Patton) makes peace with her past in order to embrace her future. Alice Troughton directed the episode penned by Aaron Helbing and Todd Helbing (FL217). Original airdate 3/29/16.