So you flushed the toilet and it came up through the shower drain .This indicates that you have a blockage in you sewer line.
Blockages often occur due to tree roots, grease that has hardend and your powder soaps that have hardened.
Mt . Everett employs both an electric cable snake and a high powered water jetter that will break through these blockages and then clean the pipe on its way out.
Mt. Everett also has a sewer camera to send down the pipe to ensure that the blockage has been removed and also check the integrity of the pipe.