Saving Catacomber after helm

I finished the dungeon but my lockpick skill was too low so I went out to talk to Martelius. He gave me the find Catacomber & castek/sword quests, but when I went back to Argimon, he took his helm & won't let me back in the dungeon.

Is there a way to still complete this quest or is Cat trapped forever??

That's the way Argimon set it up. I will die in his dungeon.

Sorry Cat! I'm sure some intrepid explorer will come for you some day.