The Green Arrow (Stephen Amell) may have killed Ra's al Ghul (Matt Nable) in "Arrow" season 3, but the League of Assassins leader is alive and kicking in the next episode of "DC's Legends of Tomorrow."

The CW released a series of photos to tease the return of Ra's al Ghul to the "Arrowverse" in the episode titled "Left Behind."

The synopsis for the episode reads, "Ray (Brandon Routh), Sara (Caity Lotz) and Kendra (Ciara Renée) are shocked after they watch the Waverider fly off without them, leaving them stranded in the '50s. After waiting months for their teammates to come back, the three realize they must move on with their lives. Ray and Kendra bond as a couple but Sara decides to return to the League of Assassins and Ra's al Ghul."

It was revealed in "Arrow" that Ra's al Ghul did not approve of Sara's relationship with his daughter Nyssa (Katrina Law) and her entry into the League of Assassins. It is not mentioned in the synopsis whether the two will have a better rapport during the 1950s era.

The episode is slated to air on Thursday, March 31.

Meanwhile, showrunner Marc Guggenheim revealed that they are already filming the first season finale of "DC's Legends of Tomorrow."

Guggenheim posted the announcement together with the cover page of the script for the finale episode, titled "Legendary," revealing that all main producers were involved in making the upcoming episode of the show.

According to the post, the concept of the episode was created by Greg Berlanti and Chris Fedak, while Guggenheim and Phil Klemmer wrote the script. The post also revealed that filming began on March 21 and is expected to wrap up on April 1.

The season finale is expected to air on May 19.