Anna is a ghost appearing in Quest for Glory: Shadows of Darkness. She was the beloved wife of Nikolai, but once ventured into the woods of Mordavia to help Dr. Cranium retrieve some Elderbury Berries, and never returned. Her ghost can only be found at night, by traveling three screens south and one screen east from the Town gate.
The Hero proved to the ghost that she had died, and soon her memory flooded back. She told the Hero who she was and without much further ado, the Hero told Nikolai that he had found his wife. Though Nikolai himself died as he sought her ghost in the woods, the two long separated lovers were reunited as spirits. They thanked the Hero for aiding them, and vanished to the afterlife.
You must be careful when looking for Anna's ghost for the first time, because two adjacent screens contain wraiths. If you stand around for too long without interacting with her, she'll vanish and you'll have to come back. Also, if you're being chased by an enemy, she won't appear.
Anna's quest is mandatory for the completion of the game, and, if you don't interact with her or with Nikolai past Day 15, you won't be able to complete it.