You need to get into East Freeport. As of Age of Discovery, if you're in The Commonlands, you can head to The Thieves' Way through a sewer grate located at -1,251.30, -83.82, 119.95 , just slightly south of The City of Freeport gates. Once inside the sewer the grate leading to East Freeport will be nearby.
In East Freeport, head into the Gorowyn Chancery near the Thieves' Way manhole.
At about -108, -41.58, -43 (the first landing of the stairwell), Yewon Martrcle will pop and attack you. Kill him.
To earn esteem with the city of Qeynos, Gil McMartin has given me a bounty to execute. I must kill Yewon Martrcle just outside of the Thieves' Way sewer exit in the alchemy shop. He uses the shop to stockpile enough poison to attempt an attack the Qeynosian water supply.
I need to execute the bounty on Yewon Martrcle just outside of the Thieves' Way sewer exit in the alchemy shop.
I need to kill Yewon Martrcle just outside of the Thieves' Way sewer exit in the alchemy shop.
I have killed Yewon Martrcle.
I have slain Yewon Martrcle.
I need to collect the bounty from Gil McMartin in the Commonlands.
I need to return to Gil McMartin to collect on the bounty