When the Green Arrow needs help tracking down a sinister bomber in Star City, speedster Barry Allen is out the door in a flash. But as the Flash saves the day with his friends on Team Arrow, a huge dimensional rift appears over his hometown of Central City--and thousands of refugees with superspeed come pouring out. Can the combined skills of Team Arrow and the Flash's friends at S.T.A.R. Labs manage the chaos long enough to stop the rift from tearing their universe apart?