Invasion! (3)

Oliver wakes up to a life where he never got on The Queen’s Gambit.  Robert and Moira Queen are alive and well.  Laurel is his loving fiancée and their wedding is imminent.  Everything seems perfect, but Oliver starts to notice small imperfections that make him question this new reality.  Meanwhile, Felicity and the recruits take on a new threat with help from The Flash and Supergirl.
Part 1 - Supergirl - S02E08
Part 2 - The Flash - S03E08
Part 3 - Arrow - S05E08
Part 4 - DC's Legends of Tomorrow - S02E07