If Monday morning had gone as planned, the Prairie Art Gallery would have been “filled with visitors, staff and a pre-school class filled with 20 children. But early in the morning, curator Robert Steven noticed one of the central roof beams had cracked and water was trickling into the south end of the building. … It was moments after city workers left the building after checking out what was going on that a third of the roof sagged and smashed to the floor.”