At the time when the bishop of Saaremaa governed the castle, all the inmates of the castle had to lead a decent life. But as it happened, there was one canon who had brought a young maiden, who was dressed as a choir boy, into the castle. It remained a secret for a long time. but once, when the bishop visited Haapsalu again, the young singer caught his attention and he ordered to find out the singer`s sex.
At the presence of canons all the suspicious rooms in the castle were searched through and it was found out that it was a girl who was wearing men`s clothes.
The bishop summoned his council and it was decided that the girl should be immured in the wall that was just under the construction. And the canon was to be put in prison where he was starved to deth. The builders left a cavity into the wall and the poor girl with a piece of bread and a mug of water was walled in. For some time her cries for help were heard.
But from that time on during the August nights of full moon she appears on the castle window.