Rose was abandoned by her family, because she was different, she was a mistake. She's a hybrid, a puppy-human hybrid, her floppy ears and tail stuck out like a sore thumb. She was kidnapped by a witch because of her rare blood type, that could be used to control and kill demons. The Winchesters go on a case that involved the witch, she was killing people and demons around the city. But when the brothers break into her home and discover Rose in the basement, locked away from the world. They realize that Rose was different and decided they couldn't let her into the world of humans, so they decide to take her in. Then they realize why she was so special in the first place and that's when everything starts coming after her.