How to continue this story? Summary?

I need it for school and it goes like this, a painter's painting was stolen, there's a video of the watcher stealing the painting. The watcher insisted he did not steal the painting, the video was again investigated and it turns out that the robber wore a mask to look like the painter, the watcher's fingerprints were seen on the wall cause the robber must have shook hands with the watcher before stealing the painting, and also the robber was shorter and fatter than the watcher thew painter concludes that it was his enemy who was unsuccessful at art stole his painting and the chase began