Sherlock Holmes [Basil Rathbone] and Dr. Watson [Nigel Bruce] find themselves far from their usual haunts when a routine conference in Canada ends with a call to action in a remote French marsh town. Lord Penrose [Paul Cavanagh] learns that his wife, the Lady Penrose, has been murdered in the village of La Morte Rouge, and Holmes, moved by a telegram from the victim sent before her death, decides to intervene despite being midway home. The pair heads into a case that blends tragedy, rumor, and an old, fearsome legend.
Arriving in the sleepy marshland settlement, they discover a community tense with superstition. The locals insist that the murder is the work of the fabled monster of La Morte Rouge, a creature that supposedly haunts the surrounding bogs. The village’s fear is palpable, and even the local doctor is drawn into the lore, remarking on the creature’s ghastly appearance. Dr. Watson describes it as “the mostly ghastly apparition... like a roaring furnace spitting fire in all directions,” a line that captures the eerie mood Holmes refuses to share with credulity alone. The detective’s keen eye quickly shifts from superstition to motive, and he spots a person of interest in the case who has endured a shadowy past.
Holmes’s investigation turns toward the village’s network of memories and wronged reputations. He rekindles a thread from a famous murder case involving the former actress Lillian Gentry, whom the late Lady Penrose may have resembled in appearance, and he identifies a practical link to the name Ramson, a master of disguise long believed dead after a prison escape. The memory of this killer’s alleged end, and the suggestion of new identities circulating in the village, leads Holmes to suspect that the real danger may be a living person still playing a deadly game. The new trail points toward Judge Brisson [Miles Mander], a man connected to the Ramson case by his earlier judgment, and whose own fate soon shadows the investigation.
Tragedy compounds as the judge is murdered, confirming Holmes’s suspicion that a concealed hand is at work. Holmes and Watson pursue Ramson to a hidden stronghold where the killer has begun to target a third person. Holmes’s pursuit culminates in a tense confrontation where Ramson holds Holmes at gunpoint, and Watson rushes in, inadvertently allowing the culprit to escape before the detective can uncover the final target. The sense of an organized plan intensifies: the expected victim is Journet, the innkeeper [Arthur Hohl], who once guarded prisoners and now seems to hold a key to the murderer’s next step. Journet, however, has vanished from view, while Ramson’s next strike deepens the village’s fear.
The plot thickens with a personal tragedy: Marie Journet [Kay Harding], Journet’s daughter, is killed by the killer for not revealing her father’s whereabouts. This brutal act jolts Holmes into action, compelling him to coax Journet back from hiding and to lure the murderer into a carefully laid trap. In a tense sequence on the marsh, Holmes and Journet stage a plan that would flush out the killer once and for all. When Ramson finally attacks Journet outdoors, Holmes—a master of disguise in his own right—steps into the fray. The struggle is fierce, and Ramson makes a rapid escape, but Journet, wielding the killer’s own weapon, a five-pronged garden weeder, turns the encounter into a climactic endgame.
As Holmes and Watson prepare to depart for Britain, Journet steps forward to honor Marie’s memory and to offer a quiet prayer at a church across the marsh. The final confrontation unfolds with dramatic precision: Ramson again closes in on his target, but the carefully laid trap pays off in an unexpected fashion, and the village’s nightmare is put to rest. The tale blends classic Holmesian deduction with a Gothic atmosphere, showcasing how a legendary fear can be manipulated by someone with a talent for disguise, manipulation, and murder.
In this tightly wound mystery, the partnership between the discerning Holmes [Basil Rathbone] and the methodical Watson [Nigel Bruce] is tested by a web of past crimes, present danger, and a haunting marshland legend. The narrative keeps its pace through a sequence of discoveries, misdirections, and revelations, culminating in a resolve that honors the victims and exposes the truth behind La Morte Rouge’s chilling rumors. The film rewards attentive viewers with a satisfying blend of deduction, suspense, and a memorable showdown on the fog-wreathed marsh.
