The Substance of Fire attempts to echo Shakespeare's King Lear, where a domineering king faces the rebellion of his children and goes mad in the process. In addition, the movie tries to explore other significant themes: survivor's guilt, The pain that a Holocaust-damaged father visits on his children, and generational family rifts. That's a lot to cover in 100 minutes, and sadly, the movie never successfully explores any of these ideas. For instance, while it's certainly plausible that Geldhart would be interested in publishing books that focus on the impact of 20th-century genocides, the movie never builds up any sympathy for Geldhart's cause. You never learn about how what impact his efforts have had over the years, from readers, peers, academics, or even friends in the publishing business. While a play can gloss over this backstory because of the immediacy of its impact on a live audience, a movie requires more explicit backstory. So, when his children turn on him, and when he descends into madness, there's little reason to care. Likewise, there's zero justification for Geldhart's adult kids despising him -- not one example by any character about how he was such a bad parent. Again, with the immediate transmission of emotions in a theater, the intensity of the performance can carry some of the load of exposition, but a film needs more spelled out. Finally, the self-destruction by the youngest son, Martin, makes no sense at all. Why would a man, ill-treated by his father, and in remission from an illness that requires him to avoid stress, volunteer to take over this ailing father's personal affairs, and thus stimulate his disease? If Martin were prone to depression and suicidality, this decision would have been understandable. But you get no hint of this prior to the Martin's ill-fated decision. As a result, you keep puzzling over this when you should be getting involved in the growing bond between Martin and his dad.