Cartwright captured and imprisoned Beth for many years so she can be friends with his sons. However, Cartwright's imprisonment and his mother's abuse of Beth led her to become the psychotic criminal "Alice."
In the present day, Cartwright had taken on the identity of Dr. Ethan Campbell and became a well-known plastic surgeon in Gotham City until his deception was discovered and was killed by Kate Kane.
August Cartwright is portrayed by John Emmett Tracy while his disguise as Ethan Campbell is portrayed by Sebastian Roché.
On the exterior, August always appeared to be an extremely good mannered person and often presented himself as an eerily calm, level-headed and patient individual, speaking with a callous voice and almost never raising his tone. However, he was actually very abusive and manipulative against both his son, Johnny, whom he raised with the belief that his face was too horrible to be ever accepted or loved by other individuals, and his young prisoner, Beth Kane, whom he cruelly threatened on more than one occasion, physically and mentally tortured her to the point that she didn't make any noise when her father and sister come to rescue her fearing that August might have killed them. He even went so far as telling Beth that her family had abandoned her, eventually "breaking" her and permanently damaging her mental sanity, which resulted in the birth of Alice.
August was an extremely intelligent individual with his skills in lying and manipulation bordering a Machiavellian personality, he managed to exploit the tailoring ability of Beth's fingers to give the finishing touch to his skin grafts masks project, which was eventually revealed to be on his own advantage as he used it to give himself the respected life he believes to deserve as Ethan Campbell. Despite this, he claimed that all of the villainous action he had done was for the sake of his son, to whom he wanted to provide a safe place in the world, yet his own deranged nature often led August to be violent and cruel even over Johnny.
A very methodical individual, August seemed to despise dirt and germs, having no qualm in ruthlessly killing a kitten in front of both Johnny and Beth, as "animals bring disease".
- August is an avid pipe smoker, which is why Beth nicknamed him the "Caterpillar".
- This is a reference to the Alice in Wonderland character named the Caterpillar, who is also known as the Hookah Smoking Caterpillar. Similar to Beth's kidnapper, the Caterpillar is mean to Alice in the story and is often very cryptic just like August's reasons for why he is holding her for most of the times seen in the flashbacks.
- August is similar to Eobard Thawne as they disguised themselves as another individual for several years; Thawne as Harrison Wells and August as Ethan Campbell.