After months of speculation and week's of teases, the epic two-night "The Flash"/"Arrow" crossover began on tonight's episode of "The Flash." Titled "Legends of Today," the first installment not only teed up the battle between Team Arrow/Team Flash and Vandal Savage (Casper Crump), but it also introduced the possibility of Oliver having a son, and Kendra being a reincarnated priestess from ancient Egypt.

MUST READ: Teddy Sears and "The Flash" EP Talk Crossover Fallout and 'Velocity 6'

First, Vandal Savage attempts to murder Kendra Saunders (Ciara Renee), and Cisco (Carlos Valdes) must put in a distress call to Barry (Grant Gustin) to rescue them. In the midst of Barry saving them, Cisco says "Thank you Barry," which immediately reveals The Flash's identity to Kendra. It was a smart way to bypass the whole "how does Kendra find out" situation. The threat of Savage inspires Barry to take Kendra and Cisco to Star City for protection. When Team Flash arrives in Star City, Barry interrupts Damien Darhk (Neal McDonough) in the middle of trying to kill Oliver (Stephen Amell). Thankfully Barry shows up in time and hilariously impresses Darhk with his super speed.

Once in the Arrow cave, Cisco throws praise and shade toward Felicity (Emily Bett Rickards) for not wiring it properly, calling her bad wiring the "death of engineering." This episode is by far the funniest of the season with Cisco and Felicity's techie chemistry bordering on hilarious. Felicity even says Vandal Savage is "hot" and "rocking a Dothraki look," -- a well timed reference to Jason Momoa's Khal Drogo from "Game of Thrones" -- when Barry shows her Savage's facial sketch, Both teams head to Oliver's house to celebrate their time together over drinks, but Savage literally crashes their party by slamming through the outside window. Barry uses his super speed to stop over a dozen arrows thrown at the team by Savage, and the Flash manages to toss both Oliver and Thea their bows. Oliver and Thea both fire off some arrows in Savage's direction -- Thea even lands the killing blow -- but Savage disappears. At this point, neither team knows who Savage is, so Cisco does decide to tell Kendra that he vibed her as beautiful bird, thus outing both his metahuman powers and hers.

While the teams discuss Cisco's vision, Malcom Merlyn (John Barrowman) barges in on the team to provide some background info on Savage. According to the League of Assassins, Savage has had his hand in thousands of years of history, dating all the way back to Genghis Khan and Julius Caesar. While Cisco wants to call him a vampire, Merlyn clarifies that Savage is an immortal. This freaks Kendra out, but Cisco manages to comfort and encourage her. Considering his own transition, Cisco is the best person to talk to her about becoming a metahuman. In the middle of their conversation, Kendra is swooped up by a man who calls her by the same name Savage used her, Shiera. He says his name is Prince Khufu and that she must "emerge." This is the first onscreen appearance of Carter Hall, also known as Hawkman (Falk Hentschel). Oliver and Barry are able to to track both Kendra and her winged kidnapper and stop Carter by using Barry's new lightning powers.

Back at the Arrow cave, both teams interrogate Carter, who claims Savage has killed both himself and Kendra over 206 times. According to Carter, Savage's life force is tethered to his and Kendra's. Merlyn returns again and warns that Savage has left Star City to look for a mystical staff. Felicity begins searching for the staff, while the rest of team helps Kendra "emerge." Unfortunately, Barry disagrees with Carter's methods and he cannot help but intervene when Kendra tries to emerge by jumping off the top of a building. Kendra is unable to tap into her powers and fly, and Carter assumes it's because something is blocking her. Even though Barry doesn't want to see Kendra fall to her death, he does encourage her to tap into her true self if she focuses on nothing else and believes in herself.

Felicity finds the location of the staff, and Barry and Oliver go to Central City in search of it. Unfortunately they are too late, because when they arrive at the staff's location, Savage is already there. Oliver and Barry impress Savage with their fighting skills, especially Barry's speed, but he still asserts that he is stronger than them. Savage then decimates the church where they are fighting, but not before Barry is able to speed Oliver to safety.

Back in Star City, Kendra and Cisco go back to the roof to test her wings again. Kendra agrees to embrace her new identity and, after hurling herself off the roof, finally takes flight. In this awesome moment, Cisco shouts and celebrates her, and he names her for the first time: Hawkgirl. The rest of the team, Laurel (Katie Cassidy), Felicity, Diggle (David Ramsey), Thea (Willa Holland), Cisco, Kendra and Carter all agree to join Oliver and Barry in Central City.

The episode's final moments focus on Barry and Oliver celebrating their brush with death at Jitters Coffee. While there, Oliver meets a young man playing with a Flash action figure. As Oliver watches the boy go back to his mother, he is shocked to see his former girlfriend (Anna Hopkins) -- the woman whom Moira Queen paid off in the flashback scenes of "Arrow" Season 2, Episode 20, "Seeing Red." In that moment Oliver wonders, "Is this my son?" Moira never told Oliver about this woman's pregnancy back in 2007, so Oliver would have no idea, but he genuinely looks stunned.

While all of these events were going on in Star and Central City, Harrison Wells (Tom Cavanagh) from Earth-2 develops a super speed serum called "Velocity 6" with Caitlin Snow (Danielle Panabaker). When Wells tries to test the serum on Jay Garrick (Teddy Sears,) Jay initially refuses. But when Patty Spivot (Shantel VanSanten) shoots Wells after mistaking him for the Wells that kills Barry's mother Jay ends up taking the serum to aid Caitlin in her attempt to save Wells' life. Jay uses his regained speed to phase through Wells' body to retrieve the bullet. You can read more about the impact of "Velocity 6" in this CBR interview with Teddy Sears and EP Andrew Kreisberg.

Some of the best moments from this episode were Cisco and Felicity's one-liners, inclduing Cisco's references to "Indiana Jones," the X-Games, and "Birdman." It was also great watching Cisco and Felicity tag team on the tech front, which cues up Cisco's best line from the episode: "Always a pleasure watching you work, Smoak." Oliver and Barry also drop some great lines about it being "your city," depending on when they were in Star City or Central City. Felicity also mimics Oliver's voice when talking about the magnetic arrows over the team intercom. She calls Oliver "love" and he calls her "honey," which the whole team can hear. It brings great levity to the characters of "Arrow," who are typically much more serious. The banter in these crossover episodes is always really fun, which makes it harder to go back to watching the shows separately following the crossover.

Some questions raised in this episode include: Why is Zoom so much faster than Barry? Is it because he is stealing speed from other speedsters like Jay Garrick? Also, is the young woman's son really Oliver's? Did she accept Moira's money and have a child with someone else, or is this Oliver's child? Lastly, now that she knows there is another Harrison Wells running around Central City, what will Patty do with that information? All will be revealed in time -- either in the second half of the crossover or in future episodes of "The Flash" and "Arrow."

"The Flash"/"Arrow" crossover continues tomorrow night with the epic conclusion at 8/7C on The CW's "Arrow.

What did you think of the crossover? Discuss it with fellow fans on the CBR Community right now!