The Ruby in the Smoke

I read this book and the other Sally Lockhart books when I was a child.  I completely forgot the title and the author.  It wasn't until I was reading Pullman's The Subtle Knife that I remembered it.  The listing of his other books was in the back of The Subtle Knife.  I was like hey that's the book I've been looking for all these years.  Well, it stood the test of my childhood.  This book was still good.  Sally's father dies a suspicious death.  While she finds clues to her father's death she gets employment from a photographer.  She also finds out about the opium addiction going around, finds out about a rare ruby, and also has a ruthless villain Mrs. Holland on her trail.  I'm looking forward to watching the tv movie that was made years ago of this. By the way, Sally is not the typical flawless heroine which kind of threw me off but at least it's different.