Coal.

Eesa and Mokhtar, who work at the mine, argue; Eesa pushes Mokhtar and makes him fall. Mokhtar's oxygen tank starts leaking without anyone noticing. Eesa finds methane and saves several people but Mokhtar dies from lack of oxygen in his bottle. Eesa is torn and must make a choice: lie, which would make him a hero, or confess everything and carry the burden of having killed Mokhtar.