Barry Allen (Grant Gustin) has spent all of Season 2 of "The Flash" trying to get fast enough to take on his murderous speedster rival Zoom (Tony Todd). However, some enemies can trump even supervillains from another universe and, as Barry tells Cisco (Carlos Valdes), S.T.A.R. Labs does not have any experience with "magic." So, when an immortal baddie named Vandal Savage (Casper Crump) shows up in Central City hell bent on killing Kendra (Ciara Renée) -- Princess Chay-Ara, he calls her -- Barry calls on the folks from "Arrow" for help in episode 8, "Legends of Today." 

Barry plucks Oliver Queen (Stephen Amell), Thea (Willa Holland) and John Diggle (David Ramsey) straight out of a battle with Damien Darhk (Neal McDonough) -- Diggle gets sick, of course -- after narrowly saving Cisco and his new girlfriend from Savage in the coffee shop. 

It takes a second for Thea to get her bearings. 

"Did I know we know the Flash?" she asks. "I didn't know we know the Flash."

Everyone meets up in Starling City and Cisco gets to help out Felicity Smoak (Emily Bett Rickards) with a couple of lab home improvement tips. Oliver, however, is a little sore that Barry brought Kendra into their world and exposed all of their identities without knowing anything about her situation. He grills Kendra, who is still getting over that her boyfriend is pals with the Flash and the Green Arrow, and forces Cisco to tell him to back off -- brave move, Cisco. Felicity suggests they regroup at her and Oliver's house over some wine to ease the tension. 

There, everyone settles down and Oliver even compliments Barry for having the maturity to reach out for help. Barry also calls out Oliver for being ... happy! Oliver says he owes it all to Felicity. The touching moment is interrupted when Savage shows up again and Oliver, Barry and Thea have to join forces to keep him at bay. An arrow from Thea knocks him off the balcony of the condo, but when Oliver peers over the edge, Savage is nowhere to be found -- spooky! Then, they get another visitor, Malcolm Merlyn (John Barrowman) -- who do their League of Shadows showing-up-out-of-nowhere thing a few times in the episode to Barry's continued befuddlement -- who is the first to know anything about the new foe. He tells them Savage is immortal. 

Meanwhile, at S.T.A.R. Labs, Wells (Tom Cavanagh) and Caitlin (Danielle Panabaker) are working on a new serum to enhance Barry's speed so he can take on Zoom. Unfortunately, while Wells is out getting materials, Patti (Shantel VanSanten) spots him. She is suspicious since, you know, Wells is supposed to be dead and all. She follows him back to S.T.A.R. Labs and when the always snarky scientist tries to explain that he is from ... another world, Patti gets skittish and shoots him just about in the heart. Caitlin calls Joe (Jesse Martin) and gets Wells on the operating table, but she needs someone immediately to stop the bullet from blocking his pulmonary artery. He needs Jay Garrick, who left in a huff earlier after expressing his disapproval of giving Barry the speed serum. 

Back in Starling City, someone shows up and kidnaps Kendra, but it is not Savage. Barry and Oliver track the culprit down and Barry gets to show off his new lightning bolt move. Meet Hawkman (Falk Hentschel).

The tied up hero explains that Savage is an immortal villain who spends his endless days hunting down him and his eternal love, Hawkgirl -- that's Kendra. Hawkman, whose real name is Carter Hall, explains that the pair are ancient Egyptian royalty who reincarnate each time Savage kills them. Hall says only he and Kendra stand a shot at facing Savage, but Barry and Oliver point out that Hawkman's and Hawkgirl's previous selves do not exactly have the best success rate. Hall challenges the heroes to do better. Cisco, on the other hand, is just upset that his new girlfriend is already in a centuries-old romance -- bummer. 

Watch a clip from "Legends of Today" below:

Hawkman tells Kendra that she needs to jump off the roof of the building to let her ancient instincts kick in so she can emerge as the winged Hawkgirl. That sounds a bit crazy to Barry, so he leaves that psychological fork in the road to Kendra and Cisco while he leaves with Oliver to go back to Central City and get an ancient weapon called the Staff of Horus before Savage can get to it -- the staff is what drew Kendra to Central City from Wisconsin. 

Of course, Barry and Oliver put up a good fight, but Savage and the staff get away; Kendra jumps off the building and becomes Hawkgirl, breaking Cisco's heart, but also blowing his mind; and at S.T.A.R. Labs, Jay shows up and takes Wells' speed serum so he can successfully remove the bullet from Wells' chest and save his life, with the one request that Wells never use the serum with Barry. The stage is set for everyone to continue the fight against Vandal Savage Wednesday night on "Arrow" (8 p.m. EST on the CW). It was certainly fun, though, to see the universes collide in the crossover episode and watch Barry and Oliver quibble about whose city they were fighting in and, thus, who was responsible for knowing how to handle their new mystical combatants. 

Plus, the end of the episode delivered a big shocker in the "Arrow" world when Oliver picked up a Flash toy and handed it to a young boy who ran off to his mother -- the unnamed pregnant woman (Anna Hopkins) Oliver’s mother once gave a $1 million to back in Season 1 as payment to leave forever and not tell Oliver. That is a very "Arrow" cliff-hanger!

What did you think of the crossover episode? Tweet your thoughts to @Ja9GarofaloTV