The Flash Talk Podcast #40- S 2 Ep 17 FLASHBACK

Barry travels back in time to when Hartley Rathaway attacked the team, and changes places with his past self in order to have Dr. Harrison Wells/Eobard Thawne help him solve the Speed Force equation. However, after a Time Wraith follows Barry to the past, Eobard deduces Barry's deception and attempts to kill him. Barry is able to convince Eobard that his plan succeeds in the future, but that in order to maintain it, he must help Barry become faster. The wraith comes to the lab, where Caitlin and Cisco are forced to accept help from a captured Hartley to deter the wraith. Afterward, the Barry from the current time arrives, forcing an explanation of the time travel event. Eobard provides the future Barry with the information needed to solve the formula, so that he can return to his time. Before he leaves, Barry tells Caitlin and Cisco to find a way to stop the wraith. As Barry prepares to make the jump through time, the wraith arrives, which forces the past timeline's Barry to intervene, so that his future self can return. Back in his time, Barry is confronted by the wraith again, but a reformed Hartley arrives with his sonic gauntlets and defeats the wraith.