" The Joining: Part 2 " is the season finale of The Batman (2004) Season 4, originally airing on May 5, 2007. The episode concludes the high-stakes alien invasion arc and marks Batman's official transition from a solo vigilante to a member of the Justice League.
Batman and J'onn attempt to infiltrate Wayne Industries to use its satellites to disrupt the Joining's signal. [S4E13] The Joining: Part 2
The episode ends with Batman joining J'onn on the Watchtower space station, where he meets other heroes: Green Lantern, The Flash, Hawkman, and Green Arrow . " The Joining: Part 2 " is the