"Northwest Mansion Mystery", also listed as "Northwest Mansion Noir", is the tenth episode in the second season of Gravity Falls, and the 30th episode overall. It premiered on February 16, 2015.
Pacifica enlists Dipper’s help to rid the Northwest Mansion of a ghost before he wreaks havoc on her family's fancy party.
- This is the only episode in which Stan does not appear, and also the first episode in which Soos does not appear (though he was planned to appear in it).
- This is also the first Gravity Falls episode with the shortened theme song.