Question: What's the deal with the puppy, and did it die in the end?
Answer: Just before the doctor was stabbed by Thomas Sharpe, his sister kills the dog she despises just off to the side and behind them-you can hear its final whimper.
Answer: The dog belonged to one of Sir Thomas' former wives. He had abandoned it on the moors, thinking it would die, but it came back to the house.
Answer: It was killed by Lucille in one of the final scenes.