the character's powers thematically and further redefined the character by introducing the Speed Force, an energy source that served as a pseudo-scientific explanation for his powers and that of other fictional speedsters within the DC Universe. Using this concept as a basis, the character's ability to tap into the Speed Force was used to expand his abilities. The character was now able to lend speed to other objects and people and create a costume directly out of Speed Force energy. Traditional powers such as the ability to vibrate through solid objects were also restored. Because of this, the Flash felt pressured into having to constantly be heroic 24/7. During this time, he joined the Justice League. The 2000s saw writer Geoff Johns revitalize the character by introducing new versions of characters such as Zoom; making significant use of the Rogues; and marrying the character to longtime girlfriend Linda Park. Other changes included restoring the Flash to a secret identity; his identity had been public since shortly after Barry Allen's death, but the traumatic events of his first battle with Zoom prompted Wally to make a deal with the Spectre to erase his identity from public knowledge (although this was initially so successful that even Wally forgot he was the Flash). During the Identity Crisis crossover, Wally and Kyle Rayner learned Dr. Light's mindwipe by the original Justice League and the cause of the villain's transformation from a dangerous serial rapist to an ineffectual buffoon. When Dr. Light vows revenge against the League, Wally realizes that the villain is again a powerful threat. He then warns the Teen Titans and Outsiders not to underestimate Dr. Light, and later joins their fight against him. In the miniseries Infinite Crisis, as a narrative device, Wally West and his family were seen leaving for an alternative reality. This allowed the character Bart Allen to become the fourth Flash and headline a relaunched third volume of the title, called The Flash: The Fastest Man Alive. The critical reaction to this new version of the Flash was mixed and Bart was killed off in the final issue of the short-lived third volume. It was decided that Wally West should return, and the JLA/JSA story "The Lightning Saga" was used to return the character to Earth along with his wife and children, who appear to have aged several years. The character next appeared in All Flash #1