Ram Dass is the Indian servant who's come back with Mr. Carrisford. We don't learn too much about him, but we don't need to: we know that he's Indian, and in this book, that's enough.
Just like this book is a little classist—that is, it think Sara is special because she's born into a higher social status than, say, Becky—it's just a wee bit racist. Check out how Mr. Carrisford describes Ram Dass as "an agile, soft-footed Oriental" (18.1) and how the narrator talks about his "dark, flashing eyes" (18.2).
In other words, because he's from India, Ram Dass supposedly has a little touch of magic about him. He's not an ordinary Englishman (not that, given the examples in the book, you would even want to be). And it's worth pointing out. We're not saying that it makes the book bad or anything, because it's just a product of its time. But it's important to note anyway.