The Wisp is a ball of energy that spawns in front of the final sign of the previous step. It is only visible when the player has drank the perk Vulture Aid. To move the wisp, the player has to interact with it within 15 seconds. If no player interacts with the Wisp within 15 seconds, it will fade away and the player will need to hit the signs again. If the player interacts with the Wisp, it will disappear and reappear somewhere else, visible through the walls if you have Vulture Aid.
When interacting with it for the first time, it will reappear at the second level of the barn, then at the second floor of the jail cell building, then to the second floor of the general store, then in the candy store and then it goes to the guillotine, where it will remain.
The player must now lure zombies near the guillotime. When close enough, the Wisp will inhabit a zombie and the player must kill it for it's energy. One by one, the player has to kill the zombie that is inhabited by the Wisp, untill the guillotine is fully powered up. Richthofen will confirm this by saying that you accidentally created a hole in the fabric of space-time along the way.