Episode begins with Dr Wells entering his special computer room, enters a log entry about Barry into his sentient AI computer. Wells notes that Barry is getting too focused on mundane uses of his power and on being a hero. He then checks the headlines of the future and notes that the future is still intact.
Dr Wells then tries to remind Barry about the research they are doing.
Barry investigates a homicide which leads to him facing the super villain of the episode who can siphon electricity, INCLUDING energy from the Flash.
Joe is also quite spooked from his encounter with the Reverse Flash.
Wells checks the future data again and now it has changed with Barry depowered, and the change is not for the better.
Barry misses his speed and laments the loss of his power.
Villain William Tock is arrested and takes over the police station.
Meanwhile Blackout goes to Star Labs to see Dr Wells, where they are busy trying to reactivate Barry's powers. Barry goes to speak to the villain, minus his Flash costume so another villain sees his face....
Tock is angry that his prison furlough was denied so he couldn't see his dying sister. Tock is clearly the Clock King as he is good at knowing times and reaction times.
Wells goes down to the cells minus his wheelchair to release the meta human that turns to steel to fight
Blackout. Wells wants him to kill him in exchange for freedom.
Steelman fights Blackout and can resist the lightning strikes to a point
Kaitlin is reluctant to lose Barry, but she aids him to regain his powers despite the risk but the attempt fails.
Steelman goes down an dies from the lightning strikes and
Blackout continues his attack. Wells admits he released Steelman and is unrepentant about his death. Wells and Barry then have a philosophic arguement while electro continues his attack.
barry's cells are regenerating but his power isn't back, Wells theorizes it is psychological rather then physical.
Clock King wounds Detective Thawne and he passes out.
Blackout is about to kill Wells when Barry reactivates his powers and defeats him via what appears to be power overload. Barry then races to the police station only to see Thawne taken away for medical assistance and that Iris has taken down the Clock King.
Black Out's body is locked in one of the cells, and Kaitlyn shows test scans that indicate Barry is now generating more power then ever, and Wells says that Barry has stepped it up a notch.
Wells and Barry talk about things and appear to reconcile.
Detective Thawne is in the hospital, enjoying his pain meds, but given that he is not rapid healing like Barry I would say that this shows that Detective Thawne is NOT the Reverse Flash.
Wells checks with his AI, Gideon. Wells makes a new log entry about Barry and comments about how Barry's attachement to people is the key to getting Barry "up to speed". Wells checks the news files and sees the future is intact again.
Episode ends with Barry on the treadmill testing his powers now to see how fast he truly is.
Wells then checks Black Out's body and takes some DNA to see how he stole Flash's powers......
Interviews with the creators of the show make it clear that the winter episodes will soon be focusing on time travel. This episode clearly is what unlocks Barry's full power, so soon he should be able to vibrate through walls, then dimensions and then breach the time barrier.
Well's behavior and attitude again tell me that he is the most likely candidate to be the Reverse Flash. Detective Thawne appears to be off the suspect list as of this episode, however he still could be the linear ancestor of the Reverse Flash.
EDIT: I just had an epiphany regarding Dr Wells. While it is true that all data points to him being the Reverse Flash, who is also slated to appear soon, it is also possible that Dr Wells is an advanced scientific being that is out to ensure that the past and future remain intact. This person would have to manipulate certain events such as the particle accelerator malfunction, having footage of Barry being struck by the lightning, his obsession with Barry and how he must be kept save to fulfill his destiny, and his contempt/disregard for most other people. Therefore taking all that into account it is quite possible that Dr Wells could be METRON.