The impression given is of a couple driving down the road, at night, I think. An animal in the road is hit by the vehicle. The passenger, wife was my impression, is distressed and wants to try and help the animal. The driver (husband?) is less than concerned and doesn't want to bother turning around to see if the creature is alright. After all, he reasons, it's only a human. The very end of the story gives the reader the understanding that the driver and passenger are aliens, the animal hit was a human being.

Please, if anyone recalls the tale and knows title and author, your help would be appreciated!

Thanks!