Lucas Kane is first directed towards Agatha by his brother, Markus. Agatha lives in a run down house full of cult-like masks and symbols. As well as a room entirely dedicated to caged crows. After Lucas gains Agatha's trust she helps him look into his unconscious memory to help him discover the Oracle.
On a return visit Lucas finds Agatha seemingly dead by the hand of the Oracle. Who has attempted to frame Lucas for the crime, this results in the games major chase sequence.
While fleeing the Oracle and the Orange Clan while in possession of the indigo child, Lucas once again comes across Agatha. Agatha asks Lucas to give her the Indigo child while revealing her true identity. Agatha is actually the Purple Clan an AI program which rivals the Orange Clan. The Purple Clan's final goal is to use the indigo prophecy to eradicate humanity and claim earth for itself.
The Purple clan is defeated in the climatic sequence by Lucas while he is in the presence of The Chroma.