The Secret of the Haunted Mirror by M. V. Carey (1974)
One of the more popular juvenile detective series of the Sixties and Seventies was The Three Investigators, created by Robert Arthur. A popular radio writer, Arthur began working in televisin in the late 1950s, working on (among lother programs) Alfred Hitchcock's television series. His association with Hitchcock led to ghost-editing some of his anthologies for Random House. In 1964, he began The Three Investigators series, also published by Random House, which tied the series in with the popular director, titling the series "Alfred Hitchcock and The Three Investigators," with Hitchcock supposedly writing and introduction to each book and appearing in the final chapter. Arthur wrote ten books in the series before his death in 1969, with the series being continued by other writers, notably Dennis Lynds (as "William Arden") (13 books), Mary Virginia Carey (15 books), Kin Platt (as "Nick West") (2 books), and Marc Brandel (3 books). In all, 43 books were published in the main series, ending in 1987; a 44th book by M. V. Carey remained unfinished/unpublished when the series ended. With the death of Alfred Hitchcock, Random House removed his name from the series. Beginning with book #31, The Mystery of the Scar-Faced Beggar by Carey, The Hitchcock character was replaced by fictional author Hector Sebastian.
[In addition, there were four Find-Your-Own Adventure books (1985-87), eleven books in a follow-up The Three Investigators -- Crimbuster series (1989-90), and 28 original German-language books never published in the U.S., under the heading "Die Drei ???" (1993-98), and there were five movies--two of them in English -- produced in Germany (2006-2009).]
The series still has a strong world-wide fan base.
So, who were The Three Investigators?
Jupiter Jones is their leader, the self-styled First Investigator. He and the two other Investigators were about 13 or 14 when the series started. Jupiter is a former cnhild actor, having gained fame as "Baby Fatso." He now lives with his, Aunt Mathilda and Uncle Titus at their salvage yard in Rocky Beach, California. An old trailer well-hidden by other salvage at the yard serves as their headquarters, and can be entered through several secret passages. The trailer is equipped with electricity, a telephone, and office furniture. Jupiter is a boy who loves solving puzzles and is willing to take risks to do so.
Pete Crenshaw is the Second Investigator, a strong and athletic boy with a degree of caution. He is sometimes distressed by Jupiter's daring.
Bob Andrews is the group's Recorder. Quiet and bookish, Bob works part-time at the local library and is relied upon for research.
Because of their successes in solving difficult mysteries, they have the tacit approval of the Rocky Beach police chief in their investigations.
Often appearing in ths series are Hans and Konrad, two Bavarian brothers who work at the salvage yard, and Worthington, an english chauffeur who began driving the bpys arund when they won a a rental Rolls Royce in a contest for a month. Hans and Konrad are both strong, doing whatever heavy lifting is needed; they often provide transport for The Three Investigators while they are doing deliveries for Uncle Titus. Worthington has taken a strong liking to the three boys and often drives them even when their one month's use of the Rolls expired; he is sometimes referred to as the Fourth Investigator by the boys.
As for The Secret of the Haunted Mirror, the 21st entry in the series...
Jupe, Pete, and Bob are helping Uncle Titus are clearing salvagables from a house schedued for demolition when they spot Worthington's Rolls Royce at a enighboring house. There's a shout of, "Stop, thief!" and they se a small man darting from the house, being chased by Worthington. Pete tries to tackle the man and got a fist slammed into his eye for his efforts. The theif got away in a nearby car.
The house, a mansion. really, belongs to a Mrs. Darnley, a woman who prefers to dress in outdated brocaded garb and to wear an old-fashioned wig. Worthington had been hired to drive her around. Mrs. Darnley, recognizing The Three Investigators and Uncle Titus from stories that Wotrthington had told her. invites them to view her collection of mirrors -- something she knew would interest Uncle Titus. A check of the premises shows that nothing appeared to be taken from the intruder. Also living with the old woman are her neice and nephew, Jean and Jeff, both about the same age as Jupe, Pete, and Bob.
The Darnley house once belonged to the famous magician Drakestar. He had died in the house and it was said to be haunted, but Mrs. Darnley has never seen or heard anything odd in the house, until the recent intruder broke into the place. Among Mrs. Darnley's collection was a mirror from the palace of the czars in St. Petersberg, a mirro with a tragic history from the California gold rush days, a mirrr that might have belnged to Queen Victoria, a mirror that belonged to Mary Todd Lincoln. and a hand mirror that belonged to Marie Antoinette.
Mrs. Darnley has another mirror, a very ugly one. It supposedly had belonged to a magician named Chiavo, who lived a couple of centuries ago. Chiavo claimed the mirror could help him see earth sprites and goblins and could help him predict the future. The mirror eventually belonged to Diego Manolas, an advisor to the president of The small island nation of Ruffino. Manolas' wife had been an old friend of Mrs. Darnley and, when he died his widow gave the mirror to her old friend. The mirror had attracted the attention of a mysterious Spaniard named Santora, who claimed to a descendant of Chiavo, Santora claimed that the mirror was cursed and would only be safe in the hands of someone with Chiavo's blood.
Something fishy seems to be going on. No one believes Santora's story, but they do believe that Santora was stunned when told told of the intruder. And then there's the image of a pale man with long white hair and bright green eyes that appeared in the cursed mirror, and then vanished.
Jupiter is convinced there is a non-supernatural explanation. Probably there was someone hiding in the house, but a search turned up nothing. Since the house had been built by a professional magician, perhaps there were secret rooms hidden there. Again, Jupiter could not find any.
In the meantime, Pete and Bob have been following Santora. The man who had tried to rob Mrs. Darnley's house shows up and attacks Santora, putting him the hospital. The trail keeps leading back to the Chiavo mirror, which must be holding an important secret, but a thorough search of the glass and its frame turns up nothing.
The Secret of the Haunted Mirror is a somewhat complicated tale that eventually involves political disruption on Ruffino. An entertaining addition to a great series.
It should be noted that when the series involves supposedly supernatural events, they are all explained rationally. However, M. V. Carey has stretched (okay, broken) this unstated rule in at least four of her books about The Three Investigators. I won't tell you if this is one of those books.