Nancy Drew discovers the hidden passage and solves the Mansion mystery by turning the haunting from an apparently supernatural threat into a problem of concealed architecture and access. A rain-ready nighttime search leads her from Nathan Gombet’s house through a steep underground route to the Turnbull mansion; later, openings into a closet and a library sofa expose how the passage connects to the sisters’ rooms and to the thefts. The discovery matters because it joins the novel’s eerie effects to a concrete mechanism that Nancy can inspect and explain.

The Nighttime Search

Nancy prepares for the investigation as a deliberate mission, not an ordinary trip to bed. After telling Rosemary Turnbull and Floretta Turnbull good night, she goes to her room without getting ready to sleep. She dresses in garments that can withstand rain, retrieves her flashlight and pistol from their hiding places, and checks that the pistol is loaded and ready for immediate use. The equipment establishes the danger she expects to face, while the flashlight anticipates the central difficulty of the search: the passage is hidden in dark, enclosed spaces.

During the search inside Gombet’s house, a woman approaches, forcing Nancy to find cover quickly. She opens a door into a small storeroom, pulls it nearly shut, and watches through a narrow crack. Almost at once, a noise comes from the cellar window; a moving light briefly rests on the storeroom door before shifting elsewhere. This interruption makes the search precarious, but it also places Nancy amid the house’s cellar spaces, where an ordinary wall and closet conceal a route that cannot be recognized by looking at the rooms as they are usually used.

The Staircase and the Route Underground

Inside a closet, Nancy notices a tiny knob with no obvious practical purpose. She twists it and hears a click, then examines the back wall: a long crack and a hollow sound suggest that the surface is not an ordinary solid wall. When she pushes the knob with all her strength, a spring clicks and the entire side of the closet wall drops away. The concealed opening reveals a steep flight of stone steps, and Nancy topples headlong down them. The mechanism is both clue and hazard: what first looks like a minor fitting releases a large section of wall and sends her into the passage before she can carefully enter it.

The stairs end at a solid wall, so discovering the route does not immediately tell Nancy how to continue. She searches it with her flashlight and finds another tiny knob, similar to the one in Gombet’s closet. Pressing it swings the wall back, allowing her through; the panel then grates shut behind her. The matching controls show that the passage is not a single accidental cavity but a deliberately constructed system of concealed entrances. For a moment, the architecture feels like something from a feudal castle, an impression Nancy connects to the strangeness of finding such a place near Cliffwood. Yet the repeated knobs and movable panels make the mystery legible as engineering rather than a supernatural intrusion.

Nancy eventually recognizes an old highboy she had seen while searching the Turnbull attic. Its familiar presence resolves her immediate uncertainty about where the route has led: she has traveled underground from Gombet’s house to the Turnbull mansion. The stairs she climbed have brought her up at the side of the house into the attic, and she concludes that other flights she passed must lead to other parts of the old building. Her earlier thorough search of the attic had not revealed the trapdoor, leaving her with a further question about how the concealed entrance had escaped notice. With no light to continue investigating, she has to wait until morning to examine the attic again.

Entrances into the Mansion

Later exploration reveals that the passage’s openings are distributed through ordinary domestic spaces. Nancy spots a metal ring, pulls it, and causes a section of wall to fall away. Behind it is a closet filled with garments. Floretta recognizes the room as her own and connects the concealed access directly to the disappearance of her silk dresses and diamond pin. The discovery gives the sisters a concrete location for at least some of the stolen valuables and explains how items could be moved through hidden spaces without an obvious entrance into the room.

Another concealed panel opens beneath the library sofa. With Rosemary holding a candle, Nancy examines the ceiling above the passage and pushes upward; the obstruction lifts, and she emerges through the sofa seat into the library. She then helps Floretta and Rosemary climb through after her. This opening explains why a search focused on visible walls and conventional doors could miss the route: an entrance can be concealed in furniture as well as behind a closet wall. The built-in domestic setting is not separate from the secret architecture; it is the disguise that makes the architecture effective.

What the Discovery Explains

The passage links Gombet’s house to the Turnbull mansion and supplies a physical means of moving between them. Its closet and wall controls, stone stairways, attic exit, garment closet, and sofa opening turn a collection of unsettling appearances into a connected spatial puzzle. Floretta’s recognition of her missing dresses and diamond pin makes the connection especially consequential: the concealed route is tied not only to the house’s eerie reputation but to the sisters’ losses.

The discovery therefore changes the terms of the mystery. Nancy’s first challenge is to enter and navigate a place designed to hide its own entrances; her next is to match its exits to recognizable rooms and objects. The familiar highboy identifies the attic, while Floretta’s garments and pin identify the closet as a place where stolen property has been concealed. The mansion’s apparent haunting yields to an explanation grounded in access, panels, and passageways. The evidence establishes the route and reveals how it could support the movement and concealment of stolen belongings, rather than depicting every theft as it occurred.