The Flash Season 1, Episode 23, titled serves as the high-stakes season finale that first aired on May 19, 2015. The episode centers on a pivotal moral and scientific dilemma: Barry Allen must decide whether to travel back in time to save his mother, Nora Allen, from being murdered by Eobard Thawne (the Reverse-Flash). Plot Summary

The finale begins with Eobard Thawne imprisoned in the S.T.A.R. Labs pipeline. He offers Barry a deal: if Barry uses the particle accelerator to reach a specific speed and creates a wormhole, he can travel back to the night of his mother's murder. In exchange, the wormhole will allow Thawne to return to his own time in the 22nd century.