It is a huge crossover of many different superheroes from different TV series. This time, they were brought together by the Harbinger, Lyra to solve the crisis on infinite earths. Harrison Nash Wells mistakenly released the Anti-Monitor. Anti-Monitor was first created by the Monitor millenniums of years ago in a time travel accident. Anti-Monitor wanted the destruction of the now existing multiverse and created a new multiverse over which he had control. It is a typical setting of the evil boss. To achieve his goal, he captured Barry Allen from Earth-90, trapped him on a treadmill and forced him to run to charge the anti-matter laser cannon. At the beginning of the film, the disaster began and earths were being wiped by the anti-matter wave after another earth. The story is average. The green arrow, Oliver Queen, sacrificed himself to save everyone else and start a new world. Sounds like a pretty cliche superhero story.
However, it means a lot to the CW channel and DC comic fans. This crossover is a restarting of the DC TV universe--it integrated the used-to-be multiple superhero earths into one as the original earth and introduce other DC TV series into this whole universe by planting them on other earths. Moreover, the most exciting of all is that the Flash from DCEU and the Flash from CW Arrow verse officially met each other in this crossover. It indicates the possibility of connections between movies and TV series.
Talk about this time’s crossover itself. The director certainly has a daring mind although the budget is really tight which can be seen in the cheap fighting scenes. What’s more, the technique of romantic irony is frequently used in this crossover. For example, the supporting players often complained about the excuse that the main characters used for attending the crossover. By using the technique it adds a lot of fun into this crossover,aka a movie consists of TV series.