Bring Proof Lord Sek is a Traitor

Can someone please help me with this quest. It is the last one I have left and I have looked on the Catacomber website and combed through this forum for answers on how to complete this quest, but I keep coming up with nothing.

I'm not entirely sure what to do. I have gone to Lord Sek's manor, and was assaulted by skeletons and female mages. I beat them all but I didn't find any proof to give Lady Nyx. I went back to ask the woman who gave the quest more info, but she wasn't no longer in the same spot. What am I supposed to be doing in this quest?

Lord Sek is not home.
Go to the Canals in the northern part of the world map and enter a Dark Tower there. Take a Shining Shield off a wall in the southeastern room and then hit a door in the same room.

Lord Sek is not home.
Go to the Canals in the northern part of the world map and enter a Dark Tower there. Take a Shining Shield off a wall in the southeastern room and then hit a door in the same room.

Thank You! I don't know who you are, but you're a saint. I have been looking around for months trying to finish this. It was so easy, I didn't even realize it. Thanks a billion