Dog

There was a house and in the house was Dog.
The house protects Dog and Dog has to protect the house.
There was no life in the house other than Dog.
But wait...
Dog's ears pointed to the left.
Squeak.
His muscles tensed.
"Have to... PROTECT.", Dog growled.
Stepping over the many things trashing the floors, he traveled though the twisting halls of the house to get to the couch room, where Owner always sits and to where Dog drags his tired body to rest.
Never onto the couch, though, for he isn't PERMITTED to.
Dog sniffed the air.
Sniff.
Sniff.
Despite the odor of rotten food, he managed to pick up a scent, his tail waggling.
"Mouse.", he barked out.
Dog began slowly walking towards the couch.
And there it was, a gray mouse sniffing a moldy sandwich left on the floor in between the couch and a wall.
"Go.... away, Mouse.", he growled, staring at the intruder.
Mouse did not move an inch, still examining the bread.
Dog got lower on his legs, ready to attack, yet somehow unable to.
Mouse finally rose its head, fixing its black, beady eyes on his.
He was visibly nervous, wondering just what would Owner do, if he saw him right now.
He would certainly YELL at dog and HIT him.
Dog whined, trying to get that vision out of his head and steady himself enough to attack the Mouse.
And then the Mouse said, "Are you following your nature or is it the memory of an order given to you by one, who is no longer here, that's keeping you waiting?"