Joe and Cisco head to Starling City to continue their investigation of Dr. Wells. While in town, the duo enlists the help of Captain Lance, and Cisco meets the Black Canary, who asks him for a favor. Meanwhile, back in Central City, Barry races to catch a meta-human named Hannibal Bates who can transform himself into every person he touches – which includes Eddie, Iris, Caitlin and even The Flash.
A former boyfriend lures Britta into joining Honda’s guerilla marketing campaign. Jeff looks to get Elroy to like him.
A mysterious recurring dream drives Castle and Beckett to seek answers about the two-month period when he went missing. But their search for the truth has deadly consequences.
Arya arrives in Braavos; Podrick and Brienne run into trouble on the road; Cersei fears for her daughter’s safety in Dorne as Ellaria Sand seeks revenge for Oberyn’s death. Stannis tempts Jon; an adviser tempts Daenerys.
Sarah pursues the missing Helena who is held in a faraway compound. Sarah must use her wiles – and acting chops – to deter a Topside investigator who threatens the Leda sisters’ lives. Meanwhile, Cosima appears to be rebounding from her illness, while Alison and Donnie face newfound financial woes. But when the menace of Castor rears its head once more, Sarah and her entire family must come together to survive.
Lance continues his mission to take down the Arrow so Felicity orders Oliver to keep a low profile. However, when a meta-human named Jake Simmons, who kills people with blasts of energy and plasma, starts terrorizing Starling City, Oliver is forced to ask Ray for help. The unlikely duo is forced to team up to save the city.
A case of disrespect hits the Heck boys when Axl — who is celebrating his milestone 21st birthday — refuses to come home and help Mike move an old freezer, and Brick begins turning into a mini-Axl by dissing Frankie with a bad attitude. Meanwhile, Sue is torn over what to do when the manager of Chop Suey USA tries to woo her away from her job at Spudsy’s.
The story of Melinda May’s transformation into “The Cavalry” is revealed as she finds herself at a crossroads in the war between Coulson and Gonzales. As Skye learns more about her true heritage from Lincoln, the truth about the Inhumans will send her in a new direction.
Barry is surprised when Felicity Smoak arrives from Starling City along with her boyfriend, Ray Palmer, who flies in as the Atom. They’ve come to visit S.T.A.R. Labs as Ray needs help with his suit. Their timing turns out to be fortuitous because it’s all hands on deck after a meta human named Brie Larvin unleashes hundreds of robotic bees to attack and kill her former co-workers, including Dr. Tina McGee. A group dinner with Barry, Felicity, Ray, Iris and Eddie turns into a disaster.
Note: Flash 1×18 takes places before Arrow 3×18.
A malicious hacker threatens to publicize everyone’s personal emails unless Greendale cancels a racist comic’s performance.