WARNING: this contains spoilers for all three books in the Different Trilogy!

Lucille O'Brien and her twin brother, Stephen, were born of Laura and Johnathan O'Brien on May 3, 2216. Her earliest memory is discovering her deranged father chained up in the basement of their home. The Flare had eaten up most of his brain and thus warped his appearance to the point where he was hardly recognizable. It's her deepest connection to the disease.

Another prominent incident is when Lucille was helping her mother cut vegetables when Stephen scared her, causing her to abruptly turn around and accidentally stab the knife through his hand. It left a scar which she later used to identify him as someone from her past while she was in the Glade. It's also the main reason why she has an acute fear of knives.

That same year, Laura was approached by two representatives from W.I.C.K.E.D about bringing her children to the facility. She declined their offer in fear of being separated from them. However, once she also began showing symptoms of the Flare, she took them to the main building herself in hopes that they'd be able to save the world.

Lucille was presented with her new name - Subject B1 - shortly after arriving. They later came up with the name Dylan, choosing it because they knew she would be famous in the future. They then attempted to make her forget her brother by sending a series of electric shocks to her brain, but she was determined not to forget. This memory was erased from her mind. It's revealed that they had also made her forget other failed experiments, but they aren't specifically stated. She was tested and discovered to not be an Immune.

This caused major complications in their tests. Because she was supposed to be the first member of Group B, she would have had to stay separate from Stephen, now named Thomas, and the other members of Group A. She spent the next nine years believing that she would go up with her friends and brother, when in reality, she would be taken into the other Maze as Thomas' equivalent.

Dylan spent her years in W.I.C.K.E.D being trained by Brent Arson to learn martial arts. Sonya was also a part of these sessions and the two quickly became friends. It's because of this that Dylan was able to survive in the Scorch and in Denver.

She quickly accelerated in Mathematics, Physics, and Health. However, because of Thomas' position, he was put into harder classes and she began to see less and less of him over the years. This made her feel inferior as Thomas' ego began to slightly overtake him.

After having a crush on Newt for several years, the two began to see each other romantically the same year the Maze Trials began. When they were saying their final goodbyes, Dylan joked about having a crush on Minho after she got the Swipe, which would later cause problems in their relationship once the Flare began twisting Newt's memories.

Dylan was operated on at an unknown point in the process so she would have the same telepathic abilities as Thomas, Teresa, and Aris. However, once it was discovered that she was in the wrong Maze, they were shut off until she needed to briefly use them in the Scorch.

The night before she was intended to be sent up to the Group B Maze, Teresa snuck her into the Box and hurriedly injected her with the Swipe so she would go up with her brother. W.I.C.K.E.D had originally designed a special, stronger version in an attempt to get rid of the twin instincts in both Thomas and Dylan. However, Teresa injected Dylan with the regular serum in hopes that she would remember her brother sooner.

She later woke up in the Box with Thomas, and the rest is history.