To play as Maria Renard, you must retrieve the prison key from a candle in the area that you are chased by a zombie bull in the default Stage 2 (do NOT take the alternate path from Stage 1). When you reach the end of the castle sewers later in the level, there will be a locked door just beside the stairs. If you did not exchange the key for any throwing items after picking it up, you can use it to open the door and rescue Maria. Complete the level as normal and the next time you restart the game, the Character Select option will be available on your save file's menu.