"It seems impossible, but Sherlock Holmes once said that when you have ruled out all other answers, what remains must be true."- Jupiter Jones (Robert Arthur's The Mystery of the Whispering Mummy, 1965)
Earlier
this month, "JJ" of The
Invisible Event wrote a great blog-post, titled "Trifecta
Perfecta – A Trio of Locked Room Riddles for Younger Readers,"
which coincided with a serendipitous discovery I made around the same
time – once again demonstrating that these detective blogs are a
hotbed for cosmic synchronicity. What I found was a practically
unknown locked room novel in the juvenile, or young adult, category.
And the publishing date places the book on the tail-end of the
genre's Golden Age!
The
Mystery of the Invisible Enemy (1959) is the fourteenth book in
the Ken Holt series by Sam and Beryl Epstein, written under the
joined pseudonym of "Bruce Campbell," consisting of eighteen
books in total. This series is purportedly "one of the very best boys' series" and the stories were
praised for their "logic and great attention to detail."
Ken
Holt is the protagonist of the series and the son of a well-known
foreign correspondent, Richard Holt of Global News, but lives
with the family of his best friend and aspiring photographer, Sandy
Allan – who runs a small-town newspaper called the Brentwood
Advance. An arrangement stemming from the first book in the
series, The Secret of Skeleton Island (1949), when the Allen
family helped "a terrified Ken Holt" locate his missing,
or kidnapped, father. In the end, the motherless Ken was invited to
come live with the Allens, which suited his foreign-correspondent
father, because the alternative would have made him the loneliest
latchkey kid in the United States.
I
should also point out that this series was obviously geared at a
slightly older readership than, let's say, The Three Investigators
by Robert
Arthur and William
Arden. One of them is that Ken and Sandy are in their late teens,
probably sixteen or seventeen years old, who drive a red convertible,
but more notably are the severity of the crimes. There are no less
than three, very serious, attempts at murdering or severely wounding
people. But more on that later.
The
Mystery of the Invisible Enemy begins very benignly: Ken and
Sandy, acting in the capacity of cub reporters, are tasked with
reporting on the annual Halloween party for the employees of the
Brentwood Foundry and Casting Company – who are about the celebrate
their tenth anniversary. Only eleven years ago, the plant was owned
by the Alborn Iron and Steel Corporation, but they deemed the
Brentwood location obsolete and abandoned the plant. A decision that
was an "absolute tragedy" for more than a hundred families
in Brentwood. Luckily, a former plant manager, Lew Collins, gathered
a group of local investors and breathed new life into the company. It
was "a tough pull," but Lew's management saw the company
grow and expand. And they were even able to sell shares in the
company.
However,
dark clouds were gathering above the company as its tenth anniversary
looms on the horizon.
Alborn
was offering to buy the company back, after it made profitable again,
which is supported by a local real-estate magnate, Bob Jennings, who
had bought himself into the company and now wanted to see a return on
his investment – resulting in "a knockdown, drag-out fight."
Collins barely held on to his company, but Alborn was underbidding
the Brentwood plant. And that's not the only problem facings Collins.
Ken and Sandy learn during the Halloween party that Collins is in the
grip of a ruthless, devious and clever extortionist.
Collins
has been diligently working an "an entirely new type of casting
machine," one that casts molten metals quicker and more
efficiently, but one day, an anonymous letter arrived with an
enclosed photograph of a section of the blue prints of the automatic
casting machine. The letter writer threatens to mail the full plans
to all of their competitors, but gives Collins the opportunity to buy
back the plans and negatives for the "reasonable price" of
$100,000! Only problem is how the letter writer had been able to
photograph the plans.
The
casting machine was designed, constructed and perfected inside a
practically hermetically sealed laboratory. A room with the only
entrance, and exit, being a door that opened on the private-office of
Collins and the only windows were steel-shuttered with locks that
were "crusted with a layer of dirty grease" that took many
months to accumulate. There were no scratches around the lock of the
door to indicate that somebody attempted to pick it.
![]() |
| Ken Holt, Reporter-Detective |
This
is where the plot shows its first signs of the series reputed
cleverness, because the locked room puzzle poses a double-edges
problem for the boys.
Logically,
the only person who could be the extortionist is one of the three
people who are in possession of a key to the laboratory, which
Collins and two of his engineers, Bruce Winters and Will Caton, but
Collins refuses to believe he has been betrayed by the boys he helped
get through college – something that, at first, appears to be the
case. However, Ken and Sandy pursuing this angle shows them to be the
type of fallible detectives in the Berkeley-Queen tradition.
I
found this to be interesting take, particular in a juvenile
mystery series, on a character who had been described as having a
brain that could work "faster than a calculating machine."
So
back to the drawing board for Ken and Sandy. What they're left with
is a genuine locked room problem, which brings them to the darkest,
most secretive, recesses of the company, but discovering the secret
of the locked laboratory nearly cast them their lives. They're
overtaken by the extortionist, tightly bound and gagged, and left to
face certain death in one of the dangerous fanning-houses of the
plant.
This
is not your typical, dime-a-dozen, spot of danger usually found in
these kind of juvenile novels, but an honest-to-god attempt at
murdering the boys. The writers make it abundantly clear that the
extortionist wants them out of the way and their predicament is
positively harrowing. Ken and Sandy are stuck their for many hours
and several attempts to find a way to escape their bonds fail
miserably. Once again, this is a part of the story where series
reputation manifest itself. The boys are gagged, but Ken came up with
a clever way to communicate with Sandy by humming the tunes of
popular songs. And how did Ken communicate to Sandy this is how they
could talk to one another? Ken simply hummed the tune of "Say It
With Music." A brilliant piece of reasoning and writing on the part
of Ken and his creators. Easily my favorite part of the book.
Of
course, this assault and attempted murder of Ken and Sandy proves to
be the downfall of the extortionist, which came on top of the assault
and attempted murder of a plant employee who was pushed off a ladder.
On a side note, the assault that left that employee in the hospital
functioned as a clue to the extortionist's schemes at the company and
he had to put that person out of the way. The only reason this
character lived to see the end of the book is that the target
audience were teenagers, but otherwise, the plot was only a couple of
steps removed from being adult (detective) fiction.
Finally,
I should give some attention to the problem of the locked laboratory.
I've seen variations of this locked room trick before, but, again,
the writers did something really clever with this trick. Ken and
Sandy realize that the locked room trick only gave the intruder
limited access to the room, which leaves them with the question how
the extortionist was able to gather a full set of photographs.
My
only complaint is that Ken almost immediately figured out this angle
to the locked room, but then again, they would find themselves in a
life-threatening predicament only moments later – which made it
necessary to get this plot-thread out of the way.
All
in all, The Mystery of the Invisible Enemy was a pleasant and
surprising discovery with a plot and story that was as good, and in
some regards even better, as the best titles from the iconic series
about The Three Investigators. So you can expect my return to
this series to take a closer look at such titles as The Clue of
the Phantom Car (1953) and The Mystery of the Vanishing
Magician (1956). I'm not sure whether, or not, they are actually
impossible crime stories, but the plot descriptions are very
promising.










