He Came... And Went

 is a quest in the Fallout: New Vegas add-on Old World Blues.

Quick walkthrough
1. Talk to Doctor Dala about the "other visitor" to Big Empty.

2. Find out the questions the other courier asked Doctor Klein.

Detailed walkthrough
After visiting the the Think Tank and talking to Doctor Klein He will tell you to talk to the other Doctors. Aftering talking to Doctor Dala you will learn that another courier travelled to the big empty and taht he was looking for another but hadn't found the right courier yet. She can't recall the questions asked but tell's you Doctor Klein Might know. Talk to Doctor Klein to learn about the other Courier.