|Complete Where Angels Fear to Tread||25||Marcus (Sanctuary)||5716 XP, Assault Rifle)|
Marcus wants you to track down someone named Kai, who was given the incorrect amount of change. The only true objective is to find Kai, so if you know where he is located, you don't have to track down his three ECHOs, which are an optional objective. You will need to fast travel to Sawtooth Cauldron as a starter, as that is where everything needed for this mission is located.
The three ECHOs are in areas rife with enemies, specifically bandits, so you'll need to either eradicate them or simply try to brave their attacks to run to the ECHO and get out of there quickly. One will be in the upper section and the other two in the lower area. You will also find Kai's body in the eastern half of the lower area, populated with threshers. The $9 will be on his body, so grab it and return to Marcus to finish the mission.