 Flash (Barry) and Impulse (Bart) are required to produce enough kinetic energy to reverse the final device, and Wally joins them to increase their chances of success, but his slower speed leads to him acting as a release valve for the excess energy and he is vaporized.The team is greatly affected by Wally's death, and Bart takes up the mantle of Kid Flash in Wally's honor.This was likely a homage to Barry Allen's death and Wally West succeeding him in "Crisis on Infinite Earths".