The title of Stephen Crane's first published war story, "A Mystery of Heroism," is also the theme of the story. Crane's theory here is that heroism is a mystery rather than a deliberate choice or thoughtful decision, but it is also something every man is capable of exhibiting.
Fred Collins, the protagonist of the story, is in the midst of a war, and the battle is violent and real. Crane delivers detail after detail to make the point that this is an active, dangerous, and on-going battle. In the midst of it, Collins suddenly develops an inexplicable thirst. He wants water, and the desire does not wane.
Across the battlefield, Collins spies a well and again expresses his desire for a drink of water. Though there is no one in the field between him and the well, the enemy is treating the empty space as a battlefield; that means it is a dangerous proposition for anyone to cross that field.
Collins's fellow soldiers are goading him to go after the water if he wants it so badly, and eventually Collins gets permission to go for some water as long as he fills up everyone's canteens.
This is a reckless act, but Collins is inexplicably unafraid of doing it. Despite that, he makes the trek across the field to the well. As he crosses the dangerous territory, Collins wonders again what it means to be a hero:
He wondered why he did not feel some keen agony of fear cutting his sense like a knife. He wondered at this, because human expression had said loudly for centuries that men should feel afraid of certain things, and that all men who did not feel this fear were phenomena--heroes.
When he realizes that what he had always seen as heroism was not as impressive and noble as he had always assumed, Collins is disappointed. He knows that he is not afraid, but he is also quite aware that he is not a hero.
Collins eventually does experience some fear; despite that, he stops and tries to give water to a fallen soldier lying in the field. It is a risky thing to do, yet he does it without hesitation.
This act is heroic despite the fact that it has no ultimate significance to the war, to the battle, or even to the fallen soldier. In fact, the bucket of water he manages to bring back to his fellow soldiers is eventually shot out of his hands and falls empty to the ground. We, like Collins, are left to ponder the idea that heroism is not so much about the results as it is about the willingness to take risks for the benefit of others. In this case, the water was not particularly helpful or useful for anyone; however, that fact does not negate the significance of his heroic journey to get it for them.
Crane's conclusion about heroism is that it is, indeed, a mysterious thing but something that a common, flawed man is capable of demonstrating.