Ten years before the game, casually, Claire wore a pale orange jacket over a black shirt and skirt, with black shoes. She also had reading glasses, and wore her hair down. In her work uniform, she wore a short white labcoat-style jacket over a black shirt with a pink tie, with green leggings.
Claire was a strong-willed young woman. She cared a lot about those close to her. She was interested in science, and was well versed in physics. She worked as a lab assistant, despite being a brilliant scientist on her own.
Ten years before Unwound Future, Claire was Layton's sweetheart, and was the assistant to the scientists who worked on the time machine, Dimitri Allen and Bill Hawks. She was chosen to be the first human subject for test running the Time Machine. However, Dimitri found a fatal error with the calculations they made, and by the time he realized Bill was going ahead with the experiment, it was too late. Bill, on the other hand, was over-confident, and since he was offered a lot of money for the experiment, success or failure, he betrayed his friend's wishes.
The time machine exploded, killing Claire and severely injuring Bill in the process.
When Layton and Luke first came to Future London, Layton saw Claire walking past them twice, and was shocked on both occasions, as he believed her to be dead. Claire appeared to take no notice of Layton and Luke, but knew they were there all along, as she saved the group from the Family in the research facility.
She initially told everyone she was Celeste, the younger sister of Claire who was searching for the truth behind Claire's death. She claimed that Claire never told Layton about her little sister because they spent the last years of her life estranged from one another. After discovering with Layton and friends the truth about 'Future Luke', she thinks of a successful plan to stop the mobile fortress using her knowledge in physics and science, and puts her life on the line to rescue an unconscious Clive from the collapsing robot.
After those events, she admitted that she was Claire, and that she didn't have long left to live. The order of events meant that she was dead and alive simultaneously; the time machine was no longer stable enough to keep her in the present.
Claire says that it is time for her to return, and that she is sorry that she can’t stay. She and Layton share a last kiss, and she turns to walk off, but Layton shouts for her to wait. She turns back, and a faint glow surrounds her body. She talks about their past, and that she will miss him and their unwound future (hence the title of the game). Layton says that he can’t let her go again, but she says that he must stay strong without her. She gives a final good-bye and walks off down an alley. Luke chases after her, only to find that she had vanished.
She had gone back to the moment the time machine exploded, sealing her fate.
It should be noted that he keeps an identical 'spare' hat in his office, one that he likely aquired shortly after receiving the first from Claire.
Claire is Layton's sweetheart. Though she worked as Dimitri's assistant, she was an excellent scientist in her own right. She was also the woman who gave Layton his beloved hat. She lost her life in a failed time-travel experiment.