Third Warning: A Mystery Story for Girls

In Short

Roy J. Snell's 1938 adventure novel follows courageous teenager Florence Huyler and her cousin Dave aboard the sixty-foot motorboat Wanderer. When forest fires threaten the pristine wilderness of Isle Royale, Michigan, the duo pitches in to haul firefighters, ferry critical supplies, and rescue stranded travelers. Along the way, they confront mystery on the open water: mysterious signals, accusations of intentional fire-setting, and a elusive youth in a crimson sweater who seems linked to every crisis. Blending rugged Great Lakes maritime lore with youthful resourcefulness, the book endures as a vivid slice of classic American depression-era regional fiction.

The Story

Florence Huyler is cruising Lake Superior aboard the motorboat Wanderer alongside her cousin, "Captain Davie," when unusual yellow clouds on the horizon signal trouble. Arriving at Isle Royale, they discover forest fires raging across the forty-mile island's primeval pine timber. Driven by a desire to preserve the island for future generations, Florence and Dave dive headfirst into the struggle, using their vessel's heavy-duty water pump to douse blazes near Siskowit and rescue imperiled camps. When their boat grounds on rocks near the flames, the weary volunteer firefighters rally to douse the surrounding shore and save the vessel from a gasoline explosion.

As the fires spread across the island, dark rumors surface that the blazes are being deliberately set. Amidst the chaos, Florence observes strange night signals across the water and crosses paths with an array of colorful figures: "Chips," a natural woodsman and leader who restores order to the chaotic firefighting efforts; a hostile rival boat operator whose past grudge against Dave's grandfather threatens their license; and a mysterious, nimble youth wearing a crimson sweater who appears at critical moments, including near a spot where a fire suddenly breaks out.

Despite the perils, Florence repeatedly shows extraordinary resourcefulness. Facing a fire advancing up a hundred-and-fifty-foot ridge at Chippewa Harbor, she devises a relay system using gasoline barrels as intermediate water reservoirs, allowing short-hose pumps to carry water up the steep incline step by step. Her heroism catches the attention of a government colonel, who requisitions the Wanderer for eight weeks at four hundred and twenty-five dollars a week, solving Florence and Dave's financial troubles and officially enlisting them in the island's defense.

The danger intensifies when Florence becomes trapped on a smoke-choked trail between walls of flame and dry, burning peat soil. She is escorted out by two rough street youths, Mike and Tony, while a rescue plane carrying her friend Jeanne flies overhead. Later, during a fierce gale, Florence and her friend Katie navigate a Thompson rowboat through mountain-high waves, using the Passage Island light and foghorn to guide them safely into harbor.

Determined to clear the name of the boy in the crimson sweater—who she realizes fought valiantly to clear a firebreak on a small island rather than set blazes—Florence travels to New York City to broadcast her story on a national radio show. The broadcast successfully reunites the young hero with his story, and Florence bids farewell to Jeanne, who departs for France. Florence then turns her face back toward Lake Superior, ready to return to the balsams, waves, and wild wilderness of Isle Royale.

How It Unfolds

The voyage begins Florence Huyler and her cousin Dave spot strange yellow clouds rolling along the Lake Superior horizon while cruising toward Isle Royale aboard the motorboat Wanderer. Upon arrival, they find forest fires threatening the island's timber and immediately deploy their boat's pump to help volunteer crews battle the flames.

Trapped by the flames After saving a camp, the Wanderer grounds on two rocks between changing winds and encroaching fire, forcing weary boys in blue overalls to douse the area near the boat's gasoline tanks until the vessel breaks free. Florence hears rumors in the darkness that someone is intentionally setting the blazes.

Rallying the defense Florence and Dave ferry supplies and messages to frightened cottagers and fishermen, eventualy rescuing a woodsman named Chips, who takes charge of mapping fire lines across Lake Ritchie and McCargo's Cove. Meanwhile, a stern government colonel requisitions the Wanderer to aid the official effort, guaranteeing the crew weekly pay that solves their financial worries.

Ingenuity on the ridge When a blaze threatens Chippewa, Florence organizes thirty young volunteers to build a water relay up a steep hill using nested gasoline barrels and small pumps. Soon after, while hiking, Florence becomes trapped in a valley of burning peat, but is led to safety through a gap in the fire wall by two streetwise boys, Mike and Tony.

Storms and phantom ships Florence and Katie get caught in a sudden Lake Superior gale while out in a rowboat, narrowly escaping destruction by navigating through pitch-black darkness to the shelter of Passage Island. They also track down the mysterious boy in the crimson sweater, who proves to be a defender of the island rather than an arsonist.

A journey to the city Florence travels to New York City to share her adventure on a national radio program, utilizing the airwaves to clear the crimson-sweatered boy's reputation. After saying goodbye to Jeanne, who leaves for France, Florence eagerly prepares to return to her beloved wilderness home on the lake.

The People

• Florence Huyler: A large, strong, and fearless young woman who possesses athletic grace and a deep love for Lake Superior. She wants to protect the primeval forests of Isle Royale from total destruction, using her quick practical intellect and calm leadership under pressure to save the island and help her friends.
• Dave ("Captain Davie"): Florence's courageous and dependable cousin who captains the Wanderer. He wants to run a successful boat operation while aiding the islanders, facing down threats from rival operators and navigate treacherous coastal waters to carry out government supply runs.
• Jeanne: Florence's delicate and imaginative French companion who loves the mystery, folklore, and beauty of the wilderness. Though easily enchanted by tales of island spirits and phantom fishermen, she stands by Florence through fire hazards before returning home to France.
• The Boy in the Crimson Sweater: An elusive, athletic youth who roams the island's isolated points. Initially suspected of being a firebug setting forest blazes, his true desire is to defend the wilderness, which he demonstrates by single-handedly chopping down balsam trees to build a firebreak.
• Chips: A natural-born director of men from the north woods who steps in during the crisis to map out strategy, coordinate patrol boats, and restore order among hundreds of scattered fire-fighters.

In Its Own Voice

Before the flames reach the shoreline, Florence and Dave contemplate the stakes of the struggle gripping the island's inhabitants:

“Beauty and a threat!” he murmured with feeling. “We must do what we can for these people and their island.”

Later, an aged veteran of the island's quiet seasons reflects on what Isle Royale represents to those who retreat to its rocky harbors:

Every summer for forty years he had made a pilgrimage to Isle Royale. His cabin stood overlooking the rocks on the Point.

As Florence wanders the streets of New York after her radio broadcast, an old newsboy offers her a word of caution about leaving the simple rhythm of the lakes behind:

“Don’t stay too long, child. Don’t stay too long.”

What It's Really About

Behind its fast-paced maritime rescues and forest-fire drama, Third Warning explores the deep value of environmental stewardship and selfless civic duty. Written during an era of growing awareness around natural conservation, the novel emphasizes that wilderness spaces like Isle Royale do not merely belong to local property owners, but form a shared heritage for all people. The story contrasts the predatory instincts of bad actors—such as reckless boat operators and malicious rumors—with the cooperative spirit of young volunteers who demand no payment for stepping into danger. It argues that true character shows itself when individuals put community service ahead of personal reward, demonstrating that practical problem-solving, courage, and clear-headedness can overcome both nature's fury and human malice.

Why Read It Today

Third Warning offers modern readers an authentic, energetic taste of vintage American juvenile adventure fiction. Snell captures the raw, unpredictable atmosphere of Lake Superior with impressive regional detail—from the cold hiss of mountain-high waves and blinding fogs around Passage Island to the pungent smoke of burning peat and balsam firs. Readers who appreciate historical outdoor survival, classic nautical lore, and spunky female protagonists will find Florence Huyler a refreshing heroine; she is practical, physically capable, and quick to take charge in an emergency without waiting to be rescued.

The narrative moves at a brisk, episodic clip, though modern readers should be aware of its period sensibilities, including light street-kid dialect ("dey iss," "scram," "gittin'") and a straightforward, unvarnished style typical of 1930s series fiction. Rather than relying on dark themes or heavy melodrama, the book relies on genuine resourcefulness, atmospheric Great Lakes settings, and a warm spirit of camaraderie. It leaves readers with a lingering appreciation for the rugged beauty of northern forests and the quiet satisfaction of a hard job well done.