Finder of Doors is the fifth and final quest given to the player by Dr. Patient. As this is a purely cutscene-based quest, no rewards are given and the player cannot choose to replay this quest once it is completed for the first time.
"The Door Finder is Turned on, it's been charged, it's ready to find the door!"
Dr. Patient instructs the player to find the secret door, which can be found by pulling a lever next to the Graveyard Ops airship. The player then enters the hatch and talks to Dr. Zomboss. After that, the player simply can proceed to the back of the zombie base where they can unlock a portal to Super Duper Brainz, Ol' Deadbeard or Z-Mech 11011-3.
Being a cutscene-based quest, there isn't anything to do in this mission. All objectives are clearly marked out and the player is instructed specifically what to do.