In the roof, I supose you need to go down the air vent instead of the skylight, but I do not find the correct words, due to my lack english... any little clue??
You're too big to fit in the vent, but smaller things will fit in there. You will need to enter the office via the skylight, but you need to get rid of the zookeeper first or he'll return you to the gorilla enclosure.
