Fallout: New Vegas/Heartache by the Number

This companion side quest concerns Rose of Sharon Cassidy, whom will be first encountered in the Mojave Outpost barracks in the south-west corner of the map. It is also related to You Can Depend on Me, as it is one of the objectives from that quest.

This quest cannot be completed alongside the quests given by the Silver Rush, as they are hostile towards her. In addition, you will need to have non-evil karma during the quest because of Cassidy's preferences.

The quest provides 500 experience points, and a choice of companion perks.

Recruitment
Once you get the appropriate job from the Crimson Caravans, you have four persuasion options which require a Barter or Speech skill of at least 50.
 * With a Barter skill of 50, throw in an additional 750 caps.
 * With a Barter skill of 75, commence a drinking contest with 12 bottles of whiskey.
 * Use the speech skill of 50, but complete a job from Ranger Jackson.
 * Use the speech skill of 75.

After recruiting her as a companion, speak with her, and one of the dialogue options should allow her going to the caravan's wreckage site.

Caravans investigation
During this part of the quest, Cassidy will want to investigate three caravan wreckages. All three are accessible from major locations by following the map marker.

The first stop is Cassidy Caravans Wreckage, located between REPCONN Headquarters and Aerotech Office Park, and also west of Grub n' Gulp Rest Stop. She considers this to be suspicious.

The second place is Griffin Wares' caravan, which has scattered loot and a few ash piles. This is located on the road leading to the north-west of New Vegas.

The third destination is Durable Dunn's Sacked Caravan, located north of the East Pump station. In this wreckage, there's also a Van Graff thug and Crimson Caravan guard.

Cassidy will recognize this as an attempt to eliminate competition, and will want to assassinate the people responsible. You can proceed with that option, or instead find a more peaceful solution.

Violent solution
The only requirement is to kill Alice McLafferty and Gloria Van Graff by any means. Of the two targets, the latter may be a bit harder, as the crier outside the Silver Rush shop will generally remove your weapons (unless you already earned their trust.)

When both targets are dead, speak with Cassidy. You will get 500 experience, and she will get the Hand of Vengeance perk, which increases her damage with guns by 15%.

Peaceful solution
Instead of killing the two targets, you can instead obtain proof about their motives. This will require a lockpicking or science skill of 75, or other means to bypass locks.

The Crimson Caravan main office has a safe. It is a medium difficulty lock, although Alice McLafferty is carrying the key.

The Silver Rush contains the evidence behind a locked door and the save. Both the door and safe require a lockpick skill of 75 to open. You can pick-pocket the key to the door from any of the Van Graff members, and there is a terminal that unlocks the safe should you have a science skill of 75.

Once you have both pieces of evidence, take them to Ranger Jackson, who is located in the Mojave Outpost where you first recruited Cassidy. Speak with Cassidy again. You will get 500 Experience, and she will receive the Calm Heart perk which gives her 50 additional hit points.