A group of people get stuck in an elevator. Soon strange things occur whilst the staff of the building try to rescue them. The light fades and people wind up dead, one after the other. Those, who are watching the CCTV in the control room soon realize that there is no other explanation other than that the devil is amongst them, punishing sinners.
Further descriptions of the plot would lead to spoilers, which is understandable since the movie is only 80 minutes long and doesn't offer much to go on about, other than the setting for a mediocre horror-film that immediately sounds somewhat intriguing, since it is completely different to haunted houses, ghosts, serial killer etc.
Judging by the premise you would feel tempted to expect a tense psychological thriller which will leave you guessing just which one of those stuck in the elevator the devil really is.

Your optimism will soon be punished with a bunch of "couldn't care less about" characters, abysmal acting and the fact that the really horrifying thing about the whole movie is that it is not horrifying at all.
In the beginning we're being told that the devil comes to Earth from time to time and takes on human form to trick and punish people. Must be boring in hell and can't wait for more handbag-thieves.
There are no terrifying scenes at all. Whenever someone gets killed, the light in the elevator goes out and when it comes back on, another corpse graces the screen. The climax in the end which you hope will put you out of your misery is replaced by a supremely unspectular anti-climax which will make you call your lawyer and sue the production company for compensation after wasting 80 precious minutes of your life.

The basic idea behind Devil is somewhat refreshing but its execution a disaster (being polite here). The editing is a joke, the scriptwriter in all likelihood a twelve year old with mental health problems and the actors should be banned from ever going near a camera again.