A group of artists who travel the world. In each hotel they stay in, they remove a painting on the wall and paint their own artwork behind it, then when they are finished they put the painting back on the wall so their own art work is unseen. Then, when the hotel room is redecorated, the picture is taken down and the people are shocked to find another person has painted a fabulous artwork behind it!
Other than this, little is known about the Secret Artist Society.
Person 1: I stayed in the hotel the other night and accidentally knocked a picture off the wall, and there was another painting on the wall behind it!
Person 2: It's time I let you in on a little secret... The Secret Artist Society!