The Reunion

The Reunion is a main quest in the Fallout: New Vegas add-on Lonesome Road.

Detailed walkthrough
You will get a radio signal from Ulysses telling you that he wants an ending to things. Go to the Canyon Wreckage, which can be reached by traveling a north by northwest path from the California Sunset Drive-in, and enter the Divide.

Upon reaching the entrance to the Divide, a message box will appear saying:

Quest stages
Die Wiedervereinigung La Reunificación Воссоединение (Lonesome Road)