Hartise, the head of Helnim's Fighters Guild, has orders for you since the rank of Swordsman. Speak to her about them, and she will reveal the existence of a defector to the Zafirbel Bay Company. She wants you to encourage said defector, a Nord named Joran, to return to the guild's employ.
The Zarfirbel Bay Company have their building right next to the Fighters Guild, and you'll find Joran inside. Ask him about the defector topic. He'll express a deep distrust of House Telvanni, one of the guild's major employers. You can respond in a couple of ways:
"If you don't come back to the Fighter's Guild, then I'll make you."
"Is there anything I can do to convince you to come back?"
Option 1 will succeed outright if your level is 10 or higher - otherwise you will enter combat with Joran and lower his health substantially, at which point he yields and agrees, albeit begrudgingly, to return to the guild. If you accidentally kill him, it will complete the quest but to Hartise's extreme displeasure. Option 2 is more viable. Asking Joran if there is anything you can do will have him comment that he's not interested in putting his neck on the line. It's enough to report back to Hartise with, so do so. She'll open up a new topic - safe work, and suggests that you talk to Lariast Batalle in town about finding Joran a cozy guard job. Lariast's store is on the west side of town. You'll need to ask him about safe work with 70+ disposition before he'll agree to take on the expense of a hired guard. Try the trader selling Telvanni Bug Musk at the north-end of town if raising disposition this high is a problem. Once Lariast has agreed to hire a guard, inform Joran. He'll readily agree.
Return to Hartise. If you strong-armed Joran into returning, she'll express a slight concern that he'll be hard to keep hold of in future, and so will only reward you with 100 gold. If you secured the new contract for Joran however, she will be much happier, rewarding you with 300 gold instead.
The following Journal ID and Index codes can be used with the Journalconsole command to manually update the quest to a certain point.
Joran the Defector (TR_m2_FG_Hartise_Joran)
Index
Finishes Quest
Journal Entry
10
A member of the Fighters Guild in Helnim, Joran, has defected to the Zafirbel Bay Company's mercenary guard. I am to go to the defector at the Zafirbel Bay Company building and persuade him to return to completing contracts for the guild.
15
Joran says he won't go back to the guild because the contracts he gets from the Telvanni are far too dangerous, and he prefers the quieter guard duty at the Zafirbel Bay Company.
20
Hartise says a local merchant, Laraist Batalle, might need a guard for his shop, and told me to persuade him to hire Joran through the guild to guard it.
25
I persuaded Lariast Batalle to purchase a guard for his shop from the Fighters Guild.
40
Joran was happy to hear about the contract with Lariast Batalle, and readily returned to working for the Guild.
50
I menaced Joran into returning to work for the guild.
100
Finishes quest
Hartise was pleased that I persuaded Joran to continue work for the guild.