When is the room of family portraits introduced in The Hound Baskervilles?

The room of family portraits is introduced in Chapter 2 of *The Hound of the Baskervilles*.

It's when Sherlock Holmes and Dr. Watson first visit Baskerville Hall and explore its history. They are shown the portraits of the Baskerville family, including the infamous Hugo Baskerville, which are presented as a chilling reminder of the legend of the hound.