I had a situation similar to this. A player was playing a Drow cleric of Elistraee (the only good drow goddess, whos mission is to make the Drow be accepted in normal lands). The players "mission" was to act as a goodwill ambassador by doing good deeds for the population and show that drow aren't necessarily guys to run from screaming.
On one particular adventure, the PC's came upon an abandoned temple. Kneeling on the ground in front of the temple entrance was a figured in robes, bent over. Hiding off to either side behind columns was (the PC's noticed after a spot check) a couple snakelike figures with bows.
The combat started and the drow filled the robed figure full of arrows immediately. Only after they won the combat did they find that the robed figure was a human female slaved chained to the ground as bait to expose people advancing on the temple.
The cleric missed a PERFECT opportunity to spread some good deeds by slaughtering the robed person instead of saving her.
That night he had a dream sent to him by Eilestraee. In the dream he was in robes and chained down and couldn't move. When he looked up he saw a figured bearing his own face charging at him, swords ginzuing away. Then it cut to a face of a beautiful drow female face, with tears running down her cheek.
Simple two second description of his dream, but it got the point across.
After several more incidents of fire first and ask questions later, the character and Eilestraee parted ways.