Barry lets his obsession with Clifford DeVoe on The Flash get the best of him in "Therefore I Am," convinced that he was the villain Team Flash has been fighting this whole season. He even gets himself a two weeks' suspension because he won't stop going after DeVoe without evidence. But, even when DeVoe finally proves him right and reveals himself as The Thinker, one big question remains: what does Clifford DeVoe want on The Flash? What does the Thinker want with Barry — why target him in the first place?
"Therefore I Am" gives fans a little bit of insight into the complicated and genius mind of Clifford DeVoe. Four years ago, he was just your average brilliant professor, with a doting, equally brilliant wife. He moved from Oxford to teach at Central City University, where he and his wife (aka The Mechanic) were focused on one mission: to expand their minds. DeVoe wanted a way to know everything in the world, and so the Mechanic created a "thinking cap" that would help expand his brain power. The only problem was that for the thinking cap to work, they would need an unlimited supply of energy. And, wouldn't you know it, that's exactly what they got when Wells/Reverse Flash turned on the Particle Accelerator. While Barry was off being hit by Dark Matter lightning, becoming the Flash, DeVoe was standing outside STAR Labs, waiting for the Accelerator to explode and unleash energy to fire up his "thinking cap." And the lightening that struck him hit directly on the cap.
Needless to say, after the night of the Particle Accelerator explosion, DeVoe was never the same. In flashbacks, "Therefore I Am" shows how he recovered from the night and suddenly has all the brain power in the world. He is solving the hardest mathematical problems in history and recalling every fact ever recorded. There is just one problem: his big brain was using up too much energy, causing his body to deteriorate at a quick pace. This is why the Thinker sits in that creepy floating chair and has his creepy thinking cap (which, it turns out, is actually a bunch of wires that connect directly into his brain) — the Mechanic designed the tech as a way to keep his body alive. While all of this explains how DeVoe became the Thinker, it still doesn't explain what he wants with Barry.
In present day, DeVoe and his wife seem to have a very specific interest in Barry and his Team. Not only did they create the bus metas as both foils for Barry and, one assumes, potential allies, they also made Barry's life complicated by filing a harassment complaint against him with the CCPD after he started questioning DeVoe. To be fair, Barry did break into their home for no reason other than his "Spidey sense," but still, it's clear DeVoe wants more than just to beat the Flash, he wants to make him suffer.
After earning a suspension and a lecture or two from Iris, Barry confronts DeVoe man to man and asks him who he really is and DeVoe confirms everything with his response: "Who's asking? Barry Allen or The Flash?" DeVoe is forthcoming with certain information — he admits to being a metahuman created the night of the Particle Accelerator explosion — but much more mysterious about the details — he won't reveal his powers, only to say that he possesses "limitless thought." Even though Barry knows who DeVoe/The Thinker is, he still doesn't really know anything. The only advantage he has right now is Team Flash, which luckily got one more member with the return of Wally West, aka Kid Flash.
The Thinker is going to let Barry and Iris get married before he unleashes the rest of his evil plan, so we won't know what exactly his endgame is for a while. Here's what we do know: The Thinker is evil, and he wants to outthink Barry. The question is why. My guess is that he needs Barry or a speedster for some kind of energy source so that he can stay alive and remain the most powerful mind on the planet. He also seems to have a desire to be the smartest man alive, and to have other people acknowledge that fact, so I wouldn't cross world domination off the list just yet.
Whatever he has planned, I think I speak for all WestAllen fans when I say, it can wait until the honeymoon is over.