This is an old classic mountain climbing film. The actors are all the best French climbers of the '50 and as such may be reguarded more as a documentary than an action or 'extreme sport' movie.It recounts a day of climbing in Chamonix. Different parties are at the refuge, they tell tales, get ready for their day, then go climbing. Some are novices on easy route, others are guides with clients, others are pro climbers putting up a new route. Things happen, small things like getting lost, big things like rescuing a snowblind climber.Talking about realism, there is no comparision with Eiger Sanction (Clint Eastwood), K2, Cliffhanger (Stalone) or The Vertical Limit.This movie showed continuously in Chamonix for about 30 years (where I saw it). The title refers to the very dark and clean mountain sky where you can sometimes see stars during the day.