Heartache by the Number

 is a quest in Fallout: New Vegas.

Quick walkthrough
Talk to Alice McLafferty in the Crimson Caravan Main Office, ask for work. After telling you there's no caravan work she'll ask you to deliver a holotape to Doctor Thomas Hilderm. He can be found inside the Terminal at Camp McCarran, just east of New Vegas. He will tell you to return to Alice.

1. Cass is drowning her sorrows at the Mojave Outpost. Her advice? Go work for the Crimson Caravan. 2. Pitch in at the Crimson Caravan company if you're looking for caravan work. 3. Alice Mclafferty will give you a Holotape to deliver to Doctor Thomas Hildern. He's located inside the main building of Camp McCarran, on the ground floor on the left. 4. Return to Cass and see if you can get her to part with the title for Cassidy Caravans. 5. Pay your respects with Cass at her caravan's grave. 6. Investigate the wreckage of the Griffin Wares caravan with Cass. 7. Track down Durable Dann's missing caravan with Cass. 8. Cass will give you an option for the next part of the quest to a) find evidence to incriminate Crimson Caravans and the Van Graffs, or b) Kill Alice McLafferty and Gloria Van Graff. 9. 10. 11. When the questline is completed, Cass will receive a) the Calm Heart perk, or b) the Heart of Vengeance perk. Calm Heart gives Cass +50 HP, while Heart of Vengeance gives Cass +15% damage with conventional weapons (i believe:please confirm)
 * Option a) Investigate the Crimson Caravan for reasons behind the attack. The evidence is located inside a locked safe in Mclafferty's office, next to her desk.
 * Option b) Assassinate McLafferty.
 * Option a) Investigate the Silver Rush in Freeside for evidence on the Van Graffs' guilt. The evidence is located inside a Hard locked safe behind a Normal(i believe: needs verifying) locked door. There is also a Hard computer terminal to unlock the safe.
 * Option b) Assassinate Gloria Van Graff
 * Option a) Take the evidence of the Caravan attacks to Jackson at the Mojave Outpost.
 * Option b) Cass will gloat about the joy of killing her enemies, simply hear her out and the quest is over.

Detailed walkthrough
When trying to get the data from the Van Graffs there are two ways that you can go about this.
 * Talk to Gloria Van Graff to start the quest Birds of a Feather, during the first part of the quest where you guard the front door of the shop four men will come up to you wanting to come into the shop. The fourth man will tell you how he's looking to replace his gun. Let him in and he will suicide bomb the inside of the shop killing everyone inside. Simon will run inside and will turn hostile towards you for destroying his place of work. There's also some pretty good loot by doing this and you keep the Van Graff combat armor and Van Graff Laser rifle. Note: Doing this will make it where you don't need to prove that they were conspiring with each other.


 * To get the note out of the safe proving the Van Graff's guilt to finish the quest the non-violent way, sneak behind Simon (the guard at the door) and steal his office key. You have to stay as far away from Simon while getting behind him otherwise he will continue facing you as you walk around him. Gloria Van Graff also has a key to the office that can be pickpocketed. It may also help to have started the Birds of a Feather quest so they are a more friendly towards to you. The safe and computer both require a 75 skill check in their respective area. Note that bringing Rose of Sharon Cassidy and talking to Jean-Baptiste Cutting will result in him killing her (Unless you have the Terrifying Presence perk). Note if you pickpocket Simon and fail but you have stolen all the loot in the black box next to him he will take those items off you as well so save game first.


 * After showing the Van Graff letter to Rose of Sharon Cassidy, you'll have to get into the Crimson Caravan safe for the other letter. You can pickpocket the key from Alice McLafferty or it is a skill level 50 lock. Pickpocketing Alice McLafferty is going to be very difficult if your sneak is low. Retrieve the letter from the safe and show it to Cass. If you kill Alice to get her key, Rose of Sharon Cassidy will only want to kill the Van Graffs and this will most likely end up with Rose of Sharon Cassidy dying as well as yourself.


 * You can mess up the sequence of events without penalty if, before you visit all the caravan sites, you take Rose of Sharon Cassidy to the Van Graffs and win the battle. The evidence will NOT be in the Van Graff's safe until after the 3rd site.  If you then take the evidence to Ranger Jackson, you can loot the Van Graff's and get the "peaceful" ending to the quest.

Bugs

 * If the PC accepts Can You Find it in Your Heart? and You Can Depend on Me before talking to Cass this quest will glitch so that the PC has "Clear the roads for Jackson..." and "(Optional) "Remove" Jackson as an obstacle..." completed and cannot progress any further.Solution Needed (PS3 Confirmed)
 * Solution: If she becomes your follower, just use the Talk To option and she will ask to go pay her respects at her caravan's grave. (PC,Xbox 360 and PS3 Confirmed)


 * The continuity of this quest will be very confusing if you previously killed the Van Graffs for the Brotherhood of Steel. Upon first meeting Cass, she will tell you that she's glad the Von Graffs have been dealt with and that all that's left is to kill McLafferty.  And, the game will trigger the "Kill McLafferty" leg of the quest, even though neither you, nor Cass herself, have any idea why she should be killed.


 * A glitch is involved due to the above event. If action is taken upon the Van Graffs before the quest, then the murder of McLafferty will not end the quest, nor change options. It will appear to be uncompleteable since the marker is still shown at her body. However, after a longer wait you can talk to Cass, thus ending the quest.

Behind the Scenes
The name of this quest is a reference to the Guy Mitchell song "Heartaches by the Numbers", which is broadcast in-game on New Vegas Radio.