Caitlin brings Barry out to a karaoke bar, hoping they both meet someone new; Cisco thinks about Hartley's dangerous proposition; Henry's snooping gets him into trouble.
After Ronnie kills a physicist, Barry and the team go after him. Joe enlists Cisco's help in the reinvestigation of Nora Allen's murder. Barry struggles with a new relationship and his duties as The Flash.
After the nuclear explosion separates Ronnie and Dr. Stein, Barry and the team believe both men are safe. Barry gets some important information about time travel.
Mark Mardon aka The Weather Wizard appears in Central City to avenge his brother's death at the hands of Joe. And Cisco realizes that Dr. Wells is hiding something.
The Flash learns that Captain Cold and Heat Wave have returned to Central City. This time Snart has brought along his sociopathic baby sister Lisa to help wreak havoc on the city.
James Jesse, a.k.a. The Trickster, once terrorized Central City twenty years ago. Now a copycat has arisen to carry on the name and resume his murderous misdeeds.
Felicity Smoak and Ray Palmer come to Central City seeking help with Ray's suit; an ex-employee releases deadly robotic bees; a group dinner does not go as planned.
Joe and Cisco visit Starling City and ask Captain Lance for help with their investigation into Dr. Wells; Laurel asks Cisco for a favor; Barry faces a new foe who can disguise himself as anyone he touches.
Barry, Caitlin, Cisco and Joe set a trap for Wells. Cisco uses himself as bait, which puts him in great danger. Meanwhile, Eddie makes a decision regarding Iris, which leaves Joe a bit unsettled.
Knowing it's a deliberate distraction from Dr. Wells, Barry and those at S.T.A.R. Labs can't help but deal with an angry, mind-controlling meta-gorilla.
When Dr. Wells reactivates the Particle Accelerator, Barry must move the imprisoned meta-humans away. To do that, he needs help, and he chooses to ask Captain Cold for it.