Phantom

Tessa never trained as a ghostbuster, but that doesn't stop her from taking a mission involving one.
Tessa's well-deserved vacation on the island after her last adventure doesn't last. Being the top agent in her organization comes with a price, and her services are soon needed to help an important supporter of the telepaths' cause with a peculiar problem: a death threat that may or may not have something to do with the house ghost.
"I don't believe in ghosts," I said. I didn't, but the idea still gave me a shiver along the spine, so I had to say that out loud.
I didn't have to read the entire dossier to understand that I had been chosen for Mission Impossible. Besides McIntosh himself, the house was infested by an incredible assortment of people; those included family members of all kinds, as well as permanent guests, occasional guests, house staff, and a couple of dogs who were the only ones I felt like writing off my list of potential murderers. I dropped the dossier on the table as instructed and added a sticky note on top of it, on which I drew a sad emoji.