The Flash episode is described as follows: “When aliens called the Dominators attack Central City, Barry (Grant Gustin) speeds over to Star City to ask the Green Arrow (guest star Stephen Amell) for help in stopping them.
“Oliver and the recruits take on a new threat with help from The Flash (guest star Grant Gustin) and Supergirl (guest star Melissa Benoist).”
“After learning the Dominators’ plan for the world, the Legends must work together with The Flash (guest star Grant Gustin), Supergirl (guest star Melissa Benoist) and Green Arrow (guest star Stephen Amell) to kill them once and for all.
Following the promo released this morning, The CW and DC Entertainment have released a new clip from tonight’s episode of The Flash, part of the Invasion! crossover event.