Getting the job at the museum and taking the Forgery training gets you the key to the Supply Room, where you find the 6th piece of the Dragon Face picture. (The Supply Room is also where the Dragon Hatch enters the museum from underground.)
When you leave the museum, it is night and the building is locked. You have to go to the docks to see the shady guy at the underground gate,which is now your way to reach the Dragon Face hatch. Find any remaining pieces of the torn dragon picture -- change the features on the hatch to match it, and you can enter the museum to prevent the theft of the famous painting.
(see related questions)
get it at night
Counterfeit Island
Night
you don't. the worker blocks you off.
it is at the museum on the top of the museum at..night.
Its a picture of the "Starry Night" by Vincent Van Gogh
Go through the underground tunnels.
hang from the light above it
Counterfeit IslandNo, Counterfeit Island is real. In fact, it'd be better named as "Art Island".
when it's night, hang on the light above it.
there is no mansion on counterfeit island
You do not die on Counterfeit Island.