The narrative starts in France, 1918, with our characters finding themselves seventy-eight feet below ground—an introduction to a striking setting. There are some impressive visual effects on display, suggesting an experience that should be visually interesting. A growing awareness of the situation they're facing emerges, and it’s both disturbing and strangely beautiful. It's an entertaining and captivating blend of science fiction and World War I themes, genuinely enjoyable to watch as events play out. The movie illustrates how far someone will go to confirm their beliefs. What's most troubling about the film's core idea is that those in opposition are also prepared to disregard basic human morality.

Source on TMDB