Sally Lockhart has just struck a man dead. Not with a weapon, though she has a pistol and probably the heart to use it. Sally killed Mr. Higgs with just three words — the seven blessings. Unfortunately, she has no idea what they mean. They were sent to her by her father, just before he drowned in the South China Seas, in a letter warning Sally of danger to come.
She had hoped that her father's colleague, Mr. Higgs, might have explained the mystery. Instead he died of fear. The only other person to witness this strange turn of events is Jim Taylor, the young assistant at the Lockhart & Selby shipping firm. With his passion for solving mysteries, Jim helps Sally begin to answer the questions surrounding her father's death. Together, they are quickly drawn into a mystery filled with opium, Chinese gangs, secrets from Sally's own past — and, at the heart of it all, the Ruby of Agrapur.
Sally's father came into possession of the Ruby many years earlier, during his time in India, and had since hidden the gem, leaving Sally a series of clues to follow. However, Sally is not the only person trying to locate the priceless stone. Her nemesis, a sinister old hag called Mrs. Holland, is desperate to get her hands on it — and will stop at nothing, including murder.
While trying to escape from Mrs. Holland, Sally crosses paths with a young photographer named Frederick Garland who takes her under his wing. Soon, he and Sally are firm friends — though a growing attraction between them may one day develop into something altogether more romantic.
Together, Sally, Fred and Jim pit their wits against the deadly plans of Mrs. Holland and her cronies. But as they are drawn deeper into the mystery, they realize that Lockhart & Selby was involved in dark and treacherous dealings in the Far East. In so doing they invoke a villain altogether more terrifying than Mrs. Holland, whom Sally will have to overcome if she is to learn the truth about her father's murder, and solve the riddle of her own identity...