He Came... And Went

He Came... And Went is a side quest in the Fallout: New Vegas add-on Old World Blues.

Detailed walkthrough
After visiting the Think Tank and speaking with Dr. Klein, he will tell the Courier to speak with the other doctors. Through dialogue options, Dr. Dala reveals that there was a different courier who traveled to Big MT. She cannot recall the questions the other courier asked, but hints that Dr. Klein might know more.

If the player character speaks to Klein, he tells them that they asked a dangerous (possibly too dangerous) question. Klein states that his memory of the event has been altered, but Dala hinted that some information might be written down somewhere.