This story starts off innocently enough as the mayor of Brentwood dedicates a new lakeside playground. The entire Allen clan were there to enjoy the event and cover it for the Advance. On their way home, Sandy and Ken opt for a short cut along the "old road", and rescue Ralph Conner from the wreck of his truck. However, this last incident in a string of bad luck, could cause the Conner Brother Trucking Company to lose its insurance coverage, hence the end of their business. It's up to Ken and Sandy to prove the conspiracy involved. Despite repeated attempts to explain the circumstances surrounding Ralph's crash, nothing concrete is achieved. When Mr. Randolph Dutton enters and offers to buy out the beleaguered company, suspicions are raised. When the name of James Tolliver becomes involved, the boys find out from Granger that the mob may be in on the action. When Pop, Bert, Sandy, and Ken investigate at the lake on the outskirts of Brentwood, the whole sordid plot begins to manifest itself. Ken and Sandy must escape a gas filled tunnel and a final battle with the forces arrayed against them, before successfully unraveling the Clue of the Phantom Car.

There is no hint of either mystery or danger in the routine assignment handed to Ken Holt and his friend, Sandy Allen, one brisk autumn evening. Sandy's father, owner and editor of the Brentwood Advance has sent them to cover a purely social event - the annual Halloween party for the employees of the Brentwood Foundry and Casting Company. Even Sandy, whose nose for mystery can sniff trouble miles away, scents nothing more dangerous in their immediate future than the possibility of eating too much of the tempting food at the festive buffet supper. But before the evening is over, Ken and Sandy find themselves agreeing to match wits with a criminal - an extortioner who quickly proves himself even more clever than the boys at first suspect, who seems to anticipate their every move to uncover his identity. It is only when their lives arc in jeopardy that the boys realize their invisible adversary is as deadly as he is clever. Trapped and helpless, Ken and Sandy face the fact that their enemy will stop at nothing to ensure the success of his criminal scheme. Readers who relish the chill of suspense and the thrill of mystery will find plenty of both in The Mystery of the Invisible Enemy.

When Ken Holt and his friend, Sandy Allen, decided to visit an archaeological dig in the small town of Gallows Cliff, Arizona, they expect to encounter nothing more dangerous than a few stone tools left behind by ancient cave men who lived a hundred centuries ago. But before their stay is twenty-four hours old, they make the startling discovery that the sleepy little village of Gallows Cliff is an important way station in a vicious smuggling operation that threatens to drag both Mexico and the United States into some international unpleasantness. Working feverishly to find the border leak that has so far defied detection by skilled investigators, Ken and Sandy soon begin to realize the crafty ability of the smuggling ring. Outwitted at almost every turn, the boys are ready to admit defeat when they hit on an idea that leads them to the ruthless criminal brain behind the smuggling operation –– and into a terrifying trap from which there seems to be no escape. How Ken and Sandy solve the most complex mystery they have ever faced will keep the reader taut with suspense until the last page of this spine-tingling, adventure-packed story.

When Ken Holt and his friend Sandy Allen drive to a bus stop in their home town to meet a visitor from Mexico, they have no idea that Ricardo Montez, through no fault of his own, will involve them in a series of dangerous events. Almost instantly, strange things begin to happen. Before more than a few hours have passed, Ken and Sandy realize that the young Mexican attracts danger as surely as sugar attracts flies. Mystery piles on mystery. What is the strange heirloom that isn't really an heirloom? Why has Ricardo's family been guarding the silver amulet for three generations? What begins innocently as a short excursion to show their new friend the wonders of New York City becomes an adventure that takes the three boys thousands of miles to a Mexican city, high in the mountains. There a desperate battle of wits develops between the boys and two sinister strangers intent on possessing the amulet –– the key to a long-forgotten treasure. How Ken and Sandy pit all their ingenuity against the criminals' diabolical cleverness, and how they uncover the amazing secret of the plumed serpent, makes another suspense-charged Ken Holt mystery.

It all starts when Ken Holt and his friend Sandy Allen spot someone trying to break into their convertible. Quick action on the boys' part scares off the would-be thief before he can do more than slash his knife into the car's top. Other things begin to happen –– things that seem to have nothing to do with the foiled robbery, but which do, somehow, appear to be linked to Ken and Sandy or to something that they mysteriously have in their possession. But what it is and who their enemies are remain unanswered questions. Ken and Sandy have just one clue: a silver scorpion cuff link. It is when the boys are following the cuff-link clue that they are led into a trap and finally discover why the criminals are after them. But by then it looks as if neither Ken nor Sandy will ever have the opportunity to reveal this information to the police. How the boys manage to avoid the fate intended for them makes this adventure one of the most action-packed and suspenseful they have ever experienced.

Ken and Sandy join an archaeological expedition in southern New Jersey near the Delaware Bay. All they expect to do is dig trenches for 3 or 4 days and not get involved in any mysteries. However, when they join the expedition, they learn that several members of the expedition have heard galloping hoof beats at night. The local people have also heard these hoof beats of what they refer to as the ghost of the galloping horse. Captain Kidd was rumored to have buried treasure in the area of the expedition, and the treasure was protected by a galloping horse. During prohibition time, the galloping ghost was heard and scared the superstitious locals away. The hoof beats were most likely produced by rum-runners who didn't want people snooping around. However, not only is there a ghost, but someone is spying on the expedition. Whoever it is, they are ruthless and will stop at nothing to sabotage the expedition. Why are they trying to sabotage the expedition? Is it a jealous archaeologist? Is it someone looking for Captain Kidd's treasure? Are rum-runners scaring people away again?

When Ken and his pal Sandy Allen board the freighter Helen Rogers, their prospects of becoming involved in a mystery are pretty remote. The long-anticipated trip to Europe, where they are to join Ken's father, a famous foreign correspondent for Global News Service, is supposed to be a well-earned vacation for the boys. But just when it seems that nothing can possibly upset the relaxing routine of the Helen Rogers, Ken and Sandy receive a radio message from Global News and abruptly find themselves involved in a crime committed over a thousand miles away. Before they are fully aware of it, the boys are matching wits with one of the wiliest adversaries of their experience - a criminal clever enough to discredit every move the boys make. In an exciting climax, deep in the ship's cargo hold, Ken and Sandy discover almost too late that their quarry is as ruthless as he is clever. Their very lives are at stake when the boys face a man determined to let nothing interfere with the success of his evil plans. For those who enjoy a suspenseful thriller, The Mystery of the Shattered Glass makes fascinating reading.

"This exciting case begins with the Allen clan attending a fund raiser at Brentwood High School. When Magnus the Magician performs his repertoire for the audience, Bert is positive he recognizes him as Chris Bell. Five years ago he saved Bert's life in Vermont, but was never properly thanked. When Sandy's brother volunteers to help out in a trick, he reveals himself and Magnus is startled and disappears later, during the show. When the Allen's make inquiries, they are stunned to find that Chris Bell is wanted for robbing a jewelry store in Hilldale, PA. When he crashes his car and is seriously injured, the Allen's vow to clear Chris' name. Ken and Sandy begin their quest at the scene of the crime, Hilldale, PA. Aside from a first -hand view of the area, nothing concrete is gained. However the the two sleuths do uncover evidence that points to Jim Turney and Harry Land as possible accomplices to Chet Rogers and Pete Wright in the robbery. This knowledge does not prevent Sandy and Ken from being imprisoned in a mine within a mountain. How the two barely escape a smoky death makes for one of the most exciting scenes in their storied careers. Fortunately, escape they do, and the guilty are brought to justice, while Chris Bell is exonerated. Bert couldn't be happier with this ending!"--newportvintagebooks.com.

The mystery begins when Ken and Sandy are driving home after covering a dog show for the Brentwood Weekly Advance. At a bus stop restaurant they offer a hitch-hiker a lift. When the boys realize that the mystery man had a bus ticket but used them for transportation anyway, the plot thickens. A private investigator, Andrew Richards, appears at the Allen's office and says that the hitch-hiker is wanted for the Plunket payroll robbery. He is identified as Fenton. Richards tells the boys that the cash from the robbery was never found, and that it may be hidden somewhere in the vicinity. Despite getting mugged by unknown assailants Ken and Sandy trail Fenton to Kenshoa Park where they are outsmarted by their elusive prey. Still, it is apparent that this park holds the key to the whole affair and that the coils of a cobra figure prominently. While searching for clues in Kenshoa, during a carnival, the sleuths run into the Rands, Hiran and Limpy. The aura of evil hangs about them. But how do they fit in with Fenton and the heist ? It is only after Ken and Sandy are held captive in a cave and outwit their cobra guards, that the fascinating truth is finally revealed.

Make Love! the Bruce Campbell Way (Digital Edition).

News reporter Ken Holt and his photographer friend, Sandy Allen, are vacationing in southern Europe. True-born newsment that they are, things just happen when they're around Minutes after they view the invaluable Knossos cylinder––the Golden Key to the language of the ancient Cretans––this prize artifact is stolen from the Athens Museum. What can they do? Nothing, Ken and Sandy decide. They're just tourists in Greece––strangers in a strange country where they don't know the language. But before twenty-four hours have passed, the boys find themselves involved in this bizarre mystery. A suspicious-acting peddler sells them a Turkish scimitar. A newspaper clipping about the daring theft of the artifact mysteriously vanishes. A bossy American librarian has an odd acquaintance. And a friend from Athens flees when he sights them in the ancient city of Dubrovnik, Yugoslavia. Unraveling the clues to a weirdly complex international gang takes as much brainwork as bravery. But the Golden Key is worth the effort. And, of course, there's a front-page story in it for the young newsmen.

When Ken and Sandy receive a fan letter from Timothy Crandall, the world's youngest millionaire, they could not know what the future held for them, because of it. Steve Granger and Richard Holt assign the two teens to obtain an interview and photos for Global News. When they arrive at Timothy's mansion in Crag's End, Long Island, the mystery begins. Where is the young recluse and what, if any role, do Ralph Walsh and his assistant Brooks have? Sandy and Ken theorize that Timothy has been kidnapped and his guardians are hiding the fact, for fear of harm to their young ward. The fact that his regular chauffeur was replaced, adds to their conviction. Following up slim leads, Sandy and Ken locate Timothy in a dingy area of New York City. There, the desperate lad tosses them his grinning tiger amulet, the same kind the boys had mailed him, in appreciation of his fan letter. However, they are captured by Andy and Jerry, the guards of the kidnapped youth. Utilizing Sandy's brawn and Ken's smarts, they escape, only to find Timothy gone. Clues point to Ice Creek, a desolate area of Long Island. There, Timothy and his governess are found and in dire straits. In a desperate battle, Sandy and Ken triumph and the mastermind is unmasked. Looking back on this case, the boys were amazed that the amulet sent to Timothy, would be vital in solving the Mystery of the Grinning Tiger.

Things start off innocently enough as Ken's father, Richard Holt comes to stay with the Allen's for the Christmas holiday. Naturally he brings gifts, one of which is for Mom Allen, an ornate iron box. This is where the mystery originates. Strange unexplained events occur at the Allen and Holt residences. There are prowlers who may be connected to Mr. Holt's investigation of the counterfeiting of ten dollar bills. When Ken and Sandy bring the iron box to Sam Morris's jewelry store in Brentwood for a minor repair, the mystery deepens. A fire is set there and it becomes apparent that someone wants that box, but why ? How is the enigmatic Amos Barrack involved ? The boys sleuthing takes them to the the docks of New York where Barrack is encountered again. Twice Ken and Sandy are held captive by the gang and while failing to escape the second time, do manage to leave clues for others to pursue. The boys are transported out to sea on a barge, where by their wits alone, are able to escape the immediate clutches of the desperate villains. Still their plight is dire, as a storm threatens to sink the barge they are still on. It is only after the boys are rescued (due to the clues they had cleverly left behind at the warehouse on the docks), that the true nature of the gangs criminal activity is revealed and the part played by the iron box is at last exposed.

While en route to Mexico City to meet Richard Holt, his son Ken and best friend Sandy Allen, pass through Laredo, Texas. There they cross the border into Mexico, where the boys witness the green flame for the first time. It becomes obvious that the lighter used to create this effect was meant for another group in a red convertible. After being warned to stay on the highway, Sandy and Ken proceed south to Mexico City, for the Pan-American Conference. When Mort Phillips is picked up as a hitch-hiker and acts suspiciously, the boys realize that they are in the midst of another mystery. When Ramon Gonzalez of the Mexican Federal Police enters the picture and Mort is identified as an FBI agent, the nature of the mystery emerges. Criminals arrive in Mexico and disappear, with new identities. Ken and Sandy naturally volunteer to assist the two law enforcement officers. It is a criminal called The Baron that the foursome are initially stalking and losing, in the interior of Mexico. However, they do capture a prisoner named Mendoza, who is canny enough to fend off their questions. Later, as Sandy and Ken continue south on their own, they stumble across a possible criminal hide-out at a hospital in Rio Clara. There they are befriended by a youth named Roberto and are then captured by the gang members Al, Joe, and George. They are taken to Dr. Gosset in the hospital at the edge of town. He is the ring leader of the gang and the one responsible for criminals leading new lives, after plastic surgery with new identities. When the three boys barricade themselves underground it is only with Ken's intense drive and Sandy's physical strength that the plot of the good Doctor is thwarted. But it is Sandy who devises a means of reaching Mort Phillips via a home made radio. It remains for the trapped youths to hold off the frenzied attacks of the gang, until help arrives. They barely do so and thereby solve The Mystery of the Green Flame.

While handling reporting assignments for his father's newspaper, young Ken Holt and his photographer friend, Sandy Allen, become involved in a world of mystery and intrigue. Ken Holt and Sandy Allen are asked by Ken's father, Richard, to do some preliminary research on a long standing land feud in Colorado. The boys drive out west in their new red convertible, given to them by a consortium of insurance companies, for solving their initial mystery, The Secret of Skeleton Island. The feud between John Raymond and Chet Wilson, in Mesa Alta, revolves around boundary markers. When a key piece of evidence disappears, it is apparent to Ken and Sandy that this dispute is also a mystery. While investigating several leads the boys have to use all their wits and strength to escape a deadly trap laid for them. But who are the villains?Aided by Bowleg, the cowboy, Ken and Sandy run down every clue in an effort to resolve this complicated mystery. It's not until the boys fight a pitched battle in a dark tunnel that the villains are unmasked, the dastardly means of their deception revealed, and "The Riddle of the Stone Elephant" is solved.**