H.G. Wells' the Invisible Man

Peter Brady risks his life when trying to save a friend from being blown-up by a new type of bomb detonator. The bomb will explode the moment a shadow falls on it, and Captain Barry Finch is trapped in a sand pit with it during a demonstration to high-ranking officers. Every time he tries to move, more sand slides towards the bomb, and any shock or shadow will set it off. It's impossible for anyone to crawl to the pit and defuse the bomb... except for The Invisible Man!