Spoilers ahead for Episode 13 of The Flash Season 4, called "True Colors." If you haven't seen the episode yet, you may want to check out some of our non-spoilery articles until you get to watch.
The Thinker has had an edge on Team Flash for almost the entire fourth season of The Flash, and it's been difficult to imagine how exactly they'll manage to defeat him. Even knowing that the cerebral inhibitor will be key to taking him down hasn't enabled them to strike a blow against him. Now, "True Colors" may have delivered the answer to the question of how the Thinker will be defeated in Season 4, and it involves an unexpected character: the Mechanic.
In "True Colors," Barry spent most of his time trying to escape Iron Heights with the bus metas to avoid being sold by Wolfe to Amunet. The Thinker decided to step in just when the escapees believed that they'd made it to freedom. He managed to absorb the powers of the four bus metas who were present, use his powers to murder Wolfe and his goons, and transfer his consciousness out of Dominic Lanse and into Becky Sharpe, a.k.a. Hazard. It was a big win for the Thinker, but not one that he fully planned with his wife.
The Mechanic was shocked that he killed Wolfe, and she protested that he wasn't supposed to go after the bus metas until they were all together. Throw in the fact that she was deliberately filling her head with a song for the entire episode to prevent the Thinker from reading her mind, and it may be safe to say that she could be the key to taking out the Thinker if her allegiances fully turn from him.
Unfortunately, if her allegiances do turn from her husband to Team Flash, it won't be without a struggle. The Thinker (now in Becky's body) realized that she was no longer 100% on board with how he was attempting to fulfill his grand plan for Central City and just went right ahead and drugged her. "True Colors" didn't reveal what exactly he dosed her with, although her face seemed to flicker with blue lights after she drank the drugged champagne, so we can be sure that it wasn't anything that can be found on the streets.
The good news is that being drugged may be what finally pushes the Mechanic into fully turning on her husband. She may love him, but they were supposed to be a team, and she made a lot of sacrifices for him. The Thinker seems to be losing the ability to work with her if he doesn't feel that he absolutely needs her. If his arrogance continues to alarm the Mechanic and she realizes that he drugged her into compliance, she could be pushed far enough to turn on her husband.
In fact, the Mechanic could be the key to the cerebral inhibitor. Team Flash hasn't constructed one themselves just yet; perhaps the Mechanic has the necessary skills to build the inhibitor. She certainly has the most knowledge about how her husband's powers work, and the construction of the inhibitor could be how Team Flash could subdue him without killing him. The Mechanic does truly love him, and stopping him without ending his life could motivate her to switch sides.
Team Flash had a pretty good ride in "True Colors," all things considered. Sure, Becky died shortly after she declared that she was ready to be a good person, but Elongated Man discovered how to use his powers and impersonate other people. He was able to pose as the not-so-dearly departed Clifford DeVoe to the judge presiding over Barry's case. A living DeVoe obviously meant that Barry couldn't have murdered him, so the judge set him free from prison. This ruse may not be able to last indefinitely. Still, it was enough to spring Barry from the clink, and Team Flash has its Flash back.