Mystery Machine Achievement

During the Oneirist's chapter, you can come across a random encounter when travelling called "Far From Home" at some point after getting the story quest to find the dagger and book. Make sure you don't avoid this encounter or you'll miss the quest "The Strangeness" for this achievement. Meet the children in Murphy, and you can then immediately head to the abandoned house, grab the key inside, and head into the basement to kill the Wraith and complete the quest (or go through all the steps of speaking to the other NPCs, your choice).