About halfway through the Graveyard level, you’re given a quest to destroy headstones. Each of them is clearly marked with orange lighting and ghostly images. However, roughly in the middle of this area, there is a spot where Jack can remove his head and enter a little mini-game. There are a handful of gravestones in a small courtyard. Striking a stone will temporarily reveal a full name. Hit a stone with a certain last name (DuPont being an example), then strike the other stone with the same last name, and they’ll disappear. Do all the pairs and the achievement will unlock.