Ariadne was a student of professor Stephen Miles, who was studying architecture in Paris. He described her as one of his "brightest and best" pupils, and when Dom Cobb came looking for a student he introduced her to him for his job offer. She assumed it was a work placement, but Cobb explained it wasn't exactly that.
Cobb introduced Ariadne to the world of shared dreaming. He explained he needed to use her architecture skills to design dreams for him to lure a subject into, in order to steal ideas. He had her design a maze in two minutes that took more than a minute to solve. He took her into a Parisian street dream, showing her how she could alter things, but the dreamer's subconscious would grow hostile. He also told her to always imagine new places, rather than drawing from memory.
Though at first reluctant, she came back and was introduced to impossible architecture by Arthur, another member of Cobb's team. She designed three levels for the task of inception on Robert Michael Fischer, without letting Cobb see what she was designing. Before the job took place, she noticed Cobb dreaming and decided to investigate what he was dreaming of. She discovered he was reliving memories of his dead wife, and realised the danger of his job. She insisted she came into the dreams with him.
When the job took place, she boarded a 747 along with the rest of the team. After being sedated by Yusuf, she was taken into the first level, the city streets. After avoiding militarised projections and a projection of Mal in the form of a train, she then discovered that if they died in the dream they would fall into Limbo. The team decided to press on, but Ariadne found out from Cobb that Mal had framed him for her death as she had become too detached from reality.
In the next level, the hotel, Arthur explained that Cobb would attempt to seduce Fischer with the Mr Charles technique. Interference from the next level up caused the projections to become suspicious, and Arthur stole a kiss from Ariadne in an attempt to remain inconspicuous. He then sedated the team and sent them to the next level down, the hospital.
When there, Ariadne watched as Dom's projection of Mal shot and killed Fischer. She and Cobb rushed inside, and realised that they had to go down another level in order to bring him back. In the next level, she found Fischer but was confronted by Mal, and Dom had her drop herself and Fischer out of a tall building in order to ride the kick up the layers and escape from Limbo. He himself would stay to find Saito, who had the power to let him back into America. She did as he said and woke up back in the plane. They team arrived in America without any problems, their job having been pulled off successfully.