Entering the museum through the Dragon Face hatch, you have three things to do.
1) Slip past the window so the Security Room guard doesn't see you
2) Hide behind the lasers in the Statue exhibit, avoid the lasers, and exit right
3) Climb up the light above the painting of "The Scream"
This may not work out well, but it is the way the quest has to be played.
it is at the museum on the top of the museum at..night.
Counterfeit Island
Go through the underground tunnels.
when it's night, hang on the light above it.
The art museum on counterfeit island opens after you go to the guy at the dock.
The Museum Fantastique is on Main Street, just left of the park where the blimp arrives on Counterfeit Island.
drink bleach, everyone knows that...
You go next to the museum and go to the balloon and leave.
To get the museum to let you in on Counterfeit Island, you have to go through the Underground Tunnel, then exit the tunnel, where it leads you to the City Docks. There will be a man waiting near the exit and he'll tell you to get a job at the museum, then meet him at night. You go to the museum and tell the guard you're there to apply for the job. He'll let you in the museum.
In the museum.
after you get a job at the museum
it is on the top level in the middle of the museum.