Just make sure you don't pull the wrong one. I thought they wanted my help, not to use me as a test subject!" Is there a key for this cage? "No, it's the levers in the center there. She's the one who put me in here! Please, let me out of here!" Why are you in this cage? "They threw me in here until they were ready to use me in one of their experiments. "See! I knew Aren wouldn't leave me in here! Hurry and get me out of this cage before they come for me!" Where are the books you stole? "I don't have them anymore. Please!" I'm here to rescue you and recover the books you stole. Help me get out of here, and I'll help you find them. I shouldn't have taken them, I know! It was stupid.
"Don't leave me here!" So, you're Orthorn? "Yes, yes! Did Arch-Mage Aren send you? He sent you to rescue me, didn't he?" I'm just here for the books you took from the College. If Orthorn survives Fellglow Keep while in the company of the Dragonborn, is not traded for the books, or if told to return to safety without accompanying them, he can be found at The Frozen Hearth in Winterhold. This avoids the fight against her and Orthorn is once again imprisoned. If Orthorn is taken as a temporary follower and survives up to the encounter with The Caller, she will offer to trade the books for Orthorn to continue using as a test subject. However, his survival is not required to recover the stolen books. They may choose whether or not to rescue Orthorn, and if they choose to do so, the option of having him become his or her temporary follower until Fellglow Keep is cleared. When initially found, Orthorn is being held captive in a cell and begs the Dragonborn for assistance. The Caller, a zealous conjurer, and leader of the rogue group of mages, was very interested in the books, in particular one of the volumes, but instead of allowing Orthorn's acceptance into the group, had him imprisoned for use in further experiments. One of the books he stole had references to the Eye of Magnus, relating a theory that there may have been something the ancient Nords were hiding under Saarthal that provoked the Elves to attack, entitled Night of Tears.
These Mages had taken a liking to him, and made him feel included, so when they left the college to continue their illegal research at Fellglow Keep, Orthorn stole some books from The Arcanaeum and took off after them, using the books as a peace offering to ingratiate himself into the clan. Orthorn was a former student at the College of Winterhold, and although not particularly talented, he got mixed in with a group of rogue mages that wished to perform experiments unsupported by the College, particularly Necromancy.