The Substance is a tale of two movies. It starts off with a really cool premise. An aging Hollywood star is given a chance to create a younger version of herself, but the process has many strings attached. Each body has to be used for exactly a week without fail and each body must be fed a fluid weekly. And then the process is only supposed to happen one time. Deviating from these rules has dire consequences as we find out later.
Besides the cool concept, the execution was pretty good. It was still an odd, quirky movie, but there was a certain logic to it as well as tension being created between the old version of Elisabeth Sparkle, played by Demi Moore, and the new version of her who is becoming a star as the new Elisabeth.
About two thirds of the way through the movie, everything falls apart. Saying that it went off the rails is not strong enough. This movie turned out to be a complete trainwreck. It was just an utter mess of nonsense and illogical actions by the characters. Also, the makers of the Substance repeatedly stated that both the new and old versions are the same person, but this wasn’t true at all. They acted as separate entities with no shared memories. The actions at the end with what the new version of Elisabeth does to the original Elisabeth was completely illogical. The culminating scene was just idiotic. The ending absolutely kills the movie. Like most Oscar nominated movies, this is not worth watching.