The End

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

Detailed walkthrough
The End is a very simple quest. All you have to do is go over to the missile contol panel after you deal with Ulysses. Then you need to select "Attempt to stop missile launch". Note: you must have rescued ED-E to accomplish this. If not, then this quest fails and leads to The Apocalypse.