Search for Dodger's stash inside the Traffic Tunnel

How do you complete "Search for Dodger's stash inside the Traffic Tunnel"?

This is step 1 of 3 in Outstanding Balance, given by Tianwen. It is completed on The Blue Gate.

• Outstanding Balance
• The Blue Gate

What are the other objectives in Outstanding Balance?

Outstanding Balance has 3 objectives in total: Search for Dodger's stash inside the Traffic Tunnel, Search Dodger's deal spot by the Pilgrim's Peak antenna and Deliver Dodger's Note to Tian Wen.