The upcoming episode of CW's "The Flash" will see the heroes of Central City taking desperate measures to defeat season 4's big bad, Clifford DeVoe, more popularly known as The Thinker (Neil Sandilands). Episode 18, titled "Lose Yourself," will feature the characters' respective plans to outmatch the enemy, although one of them might lose his own identity and turn to the dark side in the process.

According to the official synopsis for "The Flash" season 4 episode 18, Harrison Wells (Tom Cavanagh) will experience a sudden change in behavior, something that will be picked up right away by Joe (Jesse L. Martin). However, it might already be too late for Joe to warn Team Flash about Harrison's new persona, as the previous episode suggests that a villainous entity has already taken over his body.

To recall, Harrison has developed a special thinking pad that will grant the user vast intelligence to defeat The Thinker. However, this new tool is not guaranteed to have purely positive effects, as Harrison appears to have taken the Reverse-Flash character, a villain that was once associated with him in the first season.

The final scene of the previous episode shows Harrison going to a room in the headquarters, which happens to be Reverse-Flash's hidden base. Harrison puts on his latest apparatus, as the AI system, Gideon (Morena Baccarin), was awakened. Gideon called Harrison as Dr. Wells, mentioning that it has already been 1,087 days since they last saw each other.

Per Express UK, the fans are worried that Harrison will be seen once again as a villain, and the timing is just not right as Team Flash is still busy dealing with The Thinker and the bus metas.

Aside from Harrison, Ralph Dibny/Elongated Man (Hartley Sawyer) will have his own way of defeating The Thinker in "The Flash" season 4 episode 18. The trailer reveals that Ralph will be putting his own life at risk as he executes his last card against the villain. 

"The Flash" season 4 episode 18 will air next Tuesday, April 17 at 8 p.m. EST on The CW.