Koudelka is the precursor (prequel) to Sacnoth's Shadow Hearts series. Shadow Hearts takes place in the Koudelka universe and features various locales and characters from Sacnoth's debut work.

Set in 1898 in Aberystwyth, Wales, the game follows the mysterious occurrences surrounding Nemeton Monastery and the three protagonists who, by chance, are forced to investigate its dark history. The plot is split up into several storylines that all interwine with each other: the history of the monastery itself as a prison for heretics and political adversaries, where the inmates were ruthlessly tortured and killed; the tragic fate of Charlotte, who was locked up in the monastery from birth and was executed at a young age, never knowing why, who believed she was never loved and now haunts the mansion; and Ogden's past as the captain of the sunken ship The Princess Alice, his friendship with the kind Elaine and the events occurring after Elaine's death.