In "Artemis Fowl: The Time Paradox", Opal Koboi is sent back in time to try and prevent Artemis Fowl from ever becoming the criminal mastermind he eventually becomes. However, she seems to forget everything that happened during her time in the past.
The series doesn't offer a clear explanation for this. Some possible theories include:
* The time travel technology is flawed: Perhaps Opal's trip back in time caused some memory loss.
* Time travel alters the present: Maybe Opal's actions in the past, even if they failed, subtly changed the present, making her past experiences seem less relevant.
* Plot hole: It's possible that Eoin Colfer simply didn't consider how Opal's time travel would affect her in later books.
Ultimately, the series doesn't provide a definite answer. This is a question that readers have to grapple with, and it's part of what makes the series so thought-provoking.
Do you have any other questions about the Artemis Fowl series? I'd be happy to help!