Keith's Caravan Charade

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough

 * 1) Speak to Captain Parker regarding Keith's illegal activities.
 * 2) Enter Aerotech Suite 200 and find proof of his activities.
 * 3) Confront Keith.
 * 4) Return to Captain Parker

Detailed walkthrough
Offer Captain Parker a helping hand. He will ask you to find evidence that Keith is involved in drug dealing and crooked gambling, adding the note "Investigate Keith's gambling and drug operations" to your Pip-Boy. Locate Keith's deck of marked cards in a desk in the southwest corner of Aerotech Suite 200.

You can discuss the deck directly with Keith by passing a Barter check of 45, which will allow you to purchase Jet from him, and a Speech check of 60, in which he lets you in on his 'system' for winning at caravan. This does not affect the outcome of the quest.

Return to Captain Parker with your findings. He will reward you with 150 caps, you will be given the option of assisting him in arresting Keith for an extra reward. The Captain will then enter Aerotech Suite 200 and confront Keith, who taunts Parker with slights about his wife. Enraged, Captain Parker murders Keith. Talking to Captain Parker afterward will net you an additional 100 caps.

Bugs

 * If Keith is asleep when Captain Parker enters the building to confront him, Keith will go back to sleep as soon as the conversation is over causing Captain Parker to spin around in circles above the sleeping Keith. You can correct this by talking to Keith.  As soon as Keith gets up off his bed, Parker will kill him.
 * The Barter check for Keith gives 45 experience each time it is passed, even in one conversation. As of PC Version 1.1.1, this bug  can be exploited to infinitely level your character and get the Outstanding Orator achievement/trophy.
 * Rex may turn hostile against the junkies, causing Keith to flee and ending the dialogue between Keith and Captain Parker. This may be related to the bug that triggers seemingly random attacks on Rex.  If this bug affects you, reload from an earlier save and take all of the food and water items out of Rex's inventory.
 * Captain Parker may disappear from the game when entering Aerotech Suite 200 to arrest Keith. This can be fixed by reloading a saved game.
 * If Captain Parkers' main quest has not been completed, you may not be able to show him Keiths' marked cards
 * Sometimes when Captain Parker goes to confront Keith about the marked cards, Captain parker will not initiate conversation with Keith but leave as if he did. This makes it impossible to complete any of the unmarked quest. Captain Parker's dialogue will stay as if you never showed him any evidence of Keith's wrong doing but will never give you the option to show the evidence.