Nice Crime You Have Around Here

Acquisition
To obtain this mini-quest, even though it is only a conversation, you must fulfill at least one of the following conditions:
 * Give Solvitus any of the three ingredients required for the Herbalist's Tasks secondary quest.
 * Complete Blackpowder Promise, Wayward Son, or the Unbidden Rescue

Walkthrough
Just enter her house, and you two will have a lovely conversation about someone being mugged outside her house, and how fascinating it is.

Result
Learning that Merrill is fascinated with muggings, and as any other conversation you can make her get more friendship, or more rivalry.