nonton the flash season 3 episode 21

The season premiere was watched by 3.17 million people and had a 1.3 demo rating, slightly down from the second-season premiere and on par with its second-season finale. The Flash crossover episode, "Invasion!", saw a season three-high viewership of 4.15 million viewers, which was the show's largest since December 9, 2014, and a season three ...