The Flash Season 4 Episode 21 Harry and the Harrisons ( Air Date 2018-05-08 ) Genre Drama, Sci-Fi & Fantasy category. Overview "With DeVoe's Enlightenment device nearly complete, in order to disable it The Flash and his team must put their faith in an unlikely ally – Amunet Black. Meanwhile, Harry hits an all-time low when the "Council of Wells" kicks him out but then Cisco introduces him to the "Council of Harrisons."".