MAJOR SPOILERS for The Flash season 4 midseason finale ahead!
The Thinker will never be the same after The Flash midseason finale. After taking a week off to join in on this year's Arrowverse crossover, the show returned to Barry's business with The Thinker AKA Clifford Devoe. For some time now, Devoe has been whispered of as one of Barry's greatest enemies, and while he's certainly been a real pain for Team Flash, he hasn't really done enough to warrant that level of notoriety. Then came tonight's episode, "Don't Run", in which Devoe makes his move and reveals the full scope of his plan, resulting in a twist it's safe to say most viewers never saw coming.
As we learned in an earlier episode, Devoe's increased intellect comes with a price - he's dying from Amyotrophic lateral sclerosis or ALS, a motor neurone disease he carries whose effects are being sped up by his supercharged brain. To combat his symptoms, his wife, Marlize (AKA The Mechanic) creates a chair that will extend his life, but not indefinitely; eventually, Devoe will need a new body if he wants to keep on living.
In tonight's midseason finale, Devoe gets that new body, transferring his mind into that of another and outwitting Team Flash with his boldest move yet. Not to mention, he also frames Barry for the murder of Clifford Devoe, stashing his now dead and discarded body in Barry's apartment in a very convincing crime scene tableau. Just how did he manage all this? Well, it's something he's been planning from the very beginning.
To pull off this remarkable feat, we have to recall that is was The Thinker who manipulated Team Flash into bringing Barry back from the Speed Force. That was the reasoning behind the Samuroid - an adversary who would lay waste to Central City if The Flash didn't return. And when Barry does return, his exit from the Speed Force douses a bus full of people with enough dark matter that they gain superpowers and become meta-humans.
But the creation of 12 new meta-humans was a red herring. Devoe didn't need just more meta-humans, he needed a specific type of meta-human - a telepath, to be exact. (Just how he knew the incident with the bus would result in at least one of the meta-humans being a telepath isn't exactly clear, but we'll chalk that one up to him being brilliant and correctly calculating the odds.) Devoe then hires Amunet to collect the telepathic meta, a young man named Dominic, who has a brain capable of withstanding the transference of Devoe's mind and is, therefore, the perfect host.
Team Flash manages to rescue Dominic from Amunet (and remove that chunk of metal she accidentally lodged in his head), but they remain unaware of his true significance. While they're distracted by looking for The Thinker following his fight with The Flash, Amunet recaptures Dominic and delivers him to the Devoes. It's then that The Thinker makes his move - linking his brain to Dominic's via the chair's robotic arms and downloading his mind into a new, ALS-free body.
Now that Devoe's mind is in a body free of illness, The Thinker and Mechanic can continue with their plans to re-educate the world. There's no need to worry about Team Flash interfering because so far as they're aware, Deveo disappeared and Dominic isn't anyone suspicious, just another meta. And there's no need to worry about The Flash because their masterful frame-job - from the restraining order to the weapon as a wedding gift to the actual dead body dumped in Barry's apartment - practically guarantees a conviction. The only option left for Barry to clear his name (judging by the next time trailer) appears to be revealing that he's The Flash, and in forcing him to give up his secret identity, Deveo may have just become one of The Flash's greatest villains.
The Flash season 4 returns on January 16th, 2018 to The CW.