Missionaries, including Father Peregrine, go to Mars, hoping to minister to the Martians, to save them, perhaps, from sins never imagined on Earth. When they arrive, Father Peregrine asks the colonists to tell them about the Martians:
They are told not to bother. There are two kinds of Martians: one nearly extinct, and the other inhuman--blue globes of light, which may or may not be intelligent at all.
Father Peregrine is not deterred. On the chance that the spheres are intelligent, he goes into the hills of Mars to minister to the spheres. He seems to make no impression on them, but when an avalanche occurs, the spheres save him. Sure that the spheres must be intelligent, must value life, he steps off a cliff, and they rescue him; he fires a gun at his head and they dissolve the bullet into dust. This is proof enough for the other priests, so they go to build a church in the hills, to minister to balls of blue fire.
Father Peregrine insists that the symbols of the church must suit the Martians, and proposes that a glass globe filled with blue light be constructed to stand as symbol for Christ, as the man on the cross does for humans. His comrades are shocked by this, but Father Peregrine is adamant:
Eventually, when the priests attempt to give Sunday services, the globes speak to them:
So the missionaries go down to the city to minister to the humans, who still need them.