February 28: A stranger appears within Mount Justice claiming to be a time traveler and the grandson of the current Flash (Barry Allen). The boy, Bart Allen/Impulse, soon gatecrashes the Garricks' wedding anniversary party and reveals his identity. Kid Flash/Wally West arrives soon after. The party is interrupted when they all learn that a villain called Neutron is on a rampage, and the Flash, Kid Flash, and Impulse head off to stop him. Meanwhile, Red Arrow and Cheshire travel to a League of Shadows base in Tibet where they finally find the original Roy Harper. In Central City, the Flashes defeat Neutron, and Impulse secretly administers a cure to Neutron's uncontrollable power. Later, Impulse also pretends to discover that he is stranded in the present day. February 28 (Forty Years Later): Through a nonlinear narrative, it is discovered that before Impulse embarks on his voyage to the present day, he bids farewell to Neutron, fully aware that the time travel is going to be a one-way trip. After he departs (and the events of the episode take place), Neutron reverts to normal but is horrified to discover that the post-apocalyptic future around him remains unchanged.