Earlier today, CBR debuted a clip from tonight's "Flash" episode that saw Barry Allen come face to face with Barry Allen. Now, thanks to a new clip released by the CW, we know how that time travel plot came to be.

This clip from tonight's "Flash Back" episode features Barry (Grant Gustin) explaining his plan to Cisco (Carlos Valdes) and Caitlin (Danielle Panabaker) -- and it doesn't go over well. Why? Because it involves Eobard Thawne, the time-traveling Harrison Wells-impersonator that spent season one trying desperately to kill Barry. And, as Harrison Wells (Tom Cavanagh) points out, this trip could have dangerous ramifications on the timeline.

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 (#217).

And here's the clip showing Barry's time travel plan in action.

The "Flash Back" episode of "The Flash" airs tonight at 8 PM ET on the CW.