I missed the whole thing too, but I do know that Dru knew about Sharon & Brad's affair. Since Phyllis knows about the affair & was black mailing Sharon....they struggled, and Dru got caught in the cross fire. Photo's were taken that make it look like Sharon pushed Dru off the edge. But I don't know for sure.
That is all I can gather from the whole thing. Sure wish I had seen it.
Lynn