You need three pieces of evidence to get Esmerelda to unload about Evelyn.
Go upstairs to get the key to the rest of the house.
Get the book from the desk by the back door.
Get the key to the chest at the murder scene from beside the basement hatch. You may have to use Alt to pick it up.
Get the knife from the secret room in the basement.
Get the letter from the chest at the murder scene.
One you have all three, talk to either Aureus or Esmerelda.
You can also solve it by talking to Murphy, yes.
Each suspect - Aureus, Cecil, Esmerelda, Evelyn - has an object you can steal by pickpocketing, and a nearby object you can steal by sneaking. The dog will tell you which of them smells like Jake, and that's enough to move the plot along.
