You helped Jeryk tend to the trolley tracks, and in exchange, he told you the story of the Talos and the trolley.
This quest is available if you have completed the quest On Track.
Starting the Quest
Talk to Jeryk in Amh Araeng to begin the quest.
Examine the Defective Talos
Go to the quest icon on the map and check on the Unrepaired Talos. There will be a cutscene.
Slay Debitage for Their Fragments
Go southeast through the archway to exit the town, and look for quest icons in the orange circle in the minimap to find Debitage. Slay them until you have three fragments.
Deliver the Debitage Fragments
Go northwest into the town and go to the quest icon on the map. Talk to Urianger to hand over the Debitage Fragments and complete the quest. There will be a cutscene.
Next Main Scenario Quest
After you complete the quest, talk to Jeryk to accept the next quest: The Truth Hurts.