Boulder City Showdown

 is a quest in Fallout: New Vegas.

Quick walkthrough
Jessup is holding NCR troops hostage in the Boulder City Ruins. The player must stop him and free the soldiers.

1. Meet with Jessup, leader of the Great Khans in Boulder City.

2. Negotiate for the release of the NCR hostages.

3. (optional)Bribe the NCR troops into letting the Great Khans escape.

4. Tell Jessup the Great Khans are free to go.

Or

1.Kill all of the Great Khans standing guard.

2.Go inside the building (theres a door to a building where the group of Great Khans where standing) kill the 2 remaining Khans.

3. Go outside and release the hostages.

Detailed walkthrough
1. Enter the Boulder City Ruins and go into the great khans hideout. Talk to Jessup. He's the guy on the right.

2. If you have a good speech skill you can convince him to just try and walk out, shoot his way out, or release the hostages. Otherwise, refer to 3. If you don't feel like finishing this quest you don't need to. The rewards aren't great and after you talk to Jessup he tells you where the man in the checkered suit went so you don't need to do this to continue the main quest.

3. Go back and speak with Lieutenant Monroe. He says that he's been given orders to kill the Great Khans, hostages or not. If you negotiated the release of the hostages, question his integrity and he'll let the Khans go, which increases your standing with the Great Khans. If your barter skill is high enough, you can offer to give him 500 caps(or if you have 45 barter skill you can make it less) to let the Khans escape.

4. Go back to Jessup and tell him he can leave. He gives you his blessings in the hunt for the man in the checkered suit and he leaves.

Bugs
If you go to New Vegas and circumvent the entire Boulder City main-quest arc, Jessup's only dialog response will be to say Goodbye, making the quest impossible by diplomatic means.