Birds of a Feather

 is a quest in Fallout: New Vegas.

Quick walkthrough
This quest can be activated after meeting Gloria Van Graff in Freeside. She will start the Courier off with small tasks such as guarding the entrance to the Silver Rush and delivering a package. After gaining enough trust, she'll recruit you for Jean-Baptiste. Jean-Baptiste will explain he's looking for Rose of Sharon Cassidy and that he "just wants to talk to her".

Rose of Sharon Cassidy (Cass) will be down at Mojave Outpost unless you have already gotten her as a companion via another quest. To get her to follow you, you will have had to complete the jobs given from the Crimson Caravan in the quest Heartache by the Number.

Bringing Rose of Sharon Cassidy back to Jean-Baptiste will reveal his true purpose is actually to kill her. From here you can choose to let him kill her, or become hostile by saying: "Shoot her and you'll be sorry." If you choose this method you will have to kill all the guards inside the Silver Rush, including Gloria and Jean. The simple alternative is letting her die and getting paid 350 caps; losing Cass as a follower. However, if you have the Terrifying Presence perk, you can get Jean-Baptiste to back down by telling him to "Raise that gun and I'll kill everyone in this room." This effectively postpones the conclusion of this quest; it remains active/available, should the player wish to revisit Jean-Baptiste at some point later in the game.

It is possible to kill Jean-Baptiste and get away with it if you have already started this quest and want to purposefully fail it to save Cass. Simply going back to the Silver Rush, placing a few C4 around Jean and using a Stealth Boy will result in killing him without having to take out the entire shop. Alternatively, if you don't have Stealth Boys and can keep yourself hidden while picking the locked door inside the Silver Rush, that will work as a place to hide while detonating the C4. However, a stealth kill with a silenced sniper rifle also does the trick.

Detailed walkthrough
1. First you will have to guard the front door. A series of 4 NPCs will come up to you, and you must remember to allow no drunks and everyone must be searched before going in. Passing a speech check on the third customer results in being paid a bonus on top of the job's normal pay (65 Speech). The fourth NPC will be carrying a bomb. If you choose to let him in, he will blow up the entire store (and most of the items inside of the store as well), failing the quest.

2. You will need to deliver a package to a man a bit east of New Vegas. With a high speech check (75) you can get 200 caps from the man.

3. You will need to bring back Rose of Sharon Cassidy to the Silver Rush to be killed. If you bring her to Jean-Baptiste and allow her to die while in dialogue, you will lose her as a companion and fail her companion quest if you have not already completed it. However you will succeed at this quest and get a large sum of caps as a reward. (If you have a companion with you at this time you will need to split with him/her to allow Cass to follow you.)

If you end up killing Cass instead of recruiting her, the journal will update to tell you to 'Let Jean-Baptiste know that the Cassidy girl is dead'. Upon returning to him, you will still be rewarded and the quest will end as normal.

You can also choose to resist her death. This results in a fairly difficult gunfight, especially if you're low level armour-piercing rounds are highly recommended, Atomic cocktail is also useful. As soon as you threat Jean-Baptiste he'll run for the Plasma Caster on the left side of the display table. This weapon will deal you massive amounts of damage to you and your companions, in addition, every single Van Graff Thug will turn hostile on you. Your best bet is to tell Cassidy and any companions you might have with you to wait in the corridor that leads to the restrooms and quickly steal the Plasma Caster before Jean-Baptiste or any thug picks it up to use it against you. Then join your companions in the corridor and deal with the Van Graffs one by one with the Plasma Caster (Don't forget that Simon, the guard outside, will also be hostile once you exit the building, as will the Van Graff crier). You can also isolate Jean-Baptiste and focus him down first, but he has very high DTS. All the guards and his sister do not have as much, so you might need to kill them before moving on to him. Doing this will result in you failing this quest and no EXP reward, however you will be able to complete Cassidy's quest for that reward and loot all the equipment in the Silver Rush shop which can be kept for combat use or exchanged for a huge amount of caps. Or, you could complete her quest first and then lead her here to her death and complete both.

Normally you are forced to either let Cassidy die or fight the Van Graffs as soon as you initiate dialogue with Jean-Baptise, but if you have the Terrifying Presence perk, you can exit the dialogue and take more time before coming to a final decision on how to handle the situation.

4. If you choose to just let Jean-Baptiste kill Cass, then Gloria will ask you to help her with one more thing. The reward for helping her is 1000 caps and the Van Graff combat armor. What you actually have to do is kill Caesar's troops in the Abandoned Warehouse.

Bugs

 * It is possible to steal from the footlocker next to Simon and get the Van Graff Combat Armor. However once you steal it, it becomes stuck in your inventory marked as a quest item; even if Simon gives you another Van Graff armor as part of the quest. Because the armor is a quest item it doesn't actually weigh anything even though it says it weighs 25. If you complete this quest and receive another set of the armor they will stack, removing the quest item tag from the original stolen armor and giving back it's weight.


 * Also during the door guard section of the quest, if the Courier denies the fourth customer entry he will turn hostile. If the Courier deals the finishing blow in the resulting fight, Simon may freeze in place. He is supposed to walk over to the corpse, but will instead stay next to the door with his weapon out and become unresponsive to dialogue. If that doesn't happen, Simon may walk over to the corpse and ask for you to help him "move the body from the store front". He will stand there staring at the Courier, and will never speak the dialogue that triggers the fifth customer. He will, however, become hostile if you go far away from the Silver Rush, like normal. The easiest way to avoid this is to let Simon kill the fourth customer by himself - he's more than capable.

This bug may be bypassed by one of the following two options:
 * Completing the entire quest
 * Open the console, and type "SetStage 00124123 100"
 * Completing the first part of the quest
 * Enter Silver Rush and speak to Gloria Van Graff
 * While the initial dialog options are displayed, open the console and enter "ResetQuest 00124123"
 * Accept the quest regarding the package delivery.
 * Exit the Silver Rush and proceed as normal.
 * This caused you to miss the XP of the first part, but gave you the Van Graff Combat Armor. The armor is stuck, and marked a quest item, but read the bug just above (first one) to learn how to fix this.


 * More so in the second leg, when going to the point to meet up with the Strange Man, you will find him standing on a set of rocks as you grow closer to him. At a certain point, he will glitch into the rock, disappearing and unable to interact with the Courier. Yet he is still marked on your compass.