the other night guard is in bobos clown shop
In Counterfeit Island you go and find the person who stole The Scream that's the painting that gets stolen at one point. Then you must find the criminal who stole it.
The Scream
climb to the top of the lamp and the security you do the lie detector thing
the clown place by the mines
the security guard is at Bobo's clown store
BoBo's Clown Store
go down to the exit of the underground tour and meet the person who knows that the scream will be stolen
He is in the Bobo Clown Shop in Down Town
There is a painting upstairs go there click the corner where the edge is up then there is the painting that was stolen.
he is in the clown shop in counterfeit
The clown place is on counterfeit island, and you need to locate it to complete the balloon task on the is, along with some information regarding the stolen painting.
When it is stolen, you can use the museum surveillance videos (and the guard's timecard) to identify the real thief, and go looking for him with his photo.