Kristof and Alesander are finalizing their escape plans when Ursula arrives. She informs them that Julian has been released. She explains that Claudel labeled the charges against Julian as administrative irregularities and presented himself to those in power as a loyal administrator to facilitate Julian’s release.

Ursula to offers to help smuggle the four teenagers out of Paris. Kristof, moved by her courage and integrity, readily accepts her help. For him, Ursula has become a moral compass, representing a commitment to defiance in the face of overwhelming danger.

The group begins their three-day journey through the tunnels toward their first safe house in Chevilly-Larue. Alesander leads them through ancient limestone quarries and narrow passages, explaining the history of the subterranean world. To keep her mind occupied and to map their progress, Sasha builds a memory palace and recites Ovid’s Metamorphoses.

When the others ask about the story, she recounts the myth of Philomela, a woman who, after being raped and mutilated by her brother-in-law, is transformed into a nightingale and finds her voice through song. Sasha explains that it is about how people survive by becoming something new. The story connects with the group, and she reflects on the similarities between them and Ovid’s characters.

Alouette, Marguerite, and Sylvine finalize their escape plan. Marguerite prepares a wine drugged with valerian to incapacitate the guards, timing their escape for the long winter night. Their plan is to flee through a sewer tunnel located beneath the hospital’s chapel.

As they wait, Alouette finds a small pouch of spreading bellflower seeds she had hidden months earlier. Though the flower has no practical use, she feels a strange comfort in its simple existence and tucks the seeds away. After evening prayers, Marguerite successfully drugs the guards’ wine. The three women disguise themselves in stolen nuns’ robes and slip into the chapel, descending through a hidden door into the crypt and then into the sewer below.

Alouette, Marguerite, and Sylvine navigate the foul, dark sewer, which is infested with rats. As they proceed, the water level rises and Alouette, experiences sharp abdominal cramps. They reach a partially collapsed section of the tunnel and are forced to crawl through a narrow, jagged opening one by one.

After they are all through, the passage behind them collapses, cutting off any possibility of retreat. The water continues to rise, reaching their waists and making every step a struggle. Just as their strength is failing, they see moonlight ahead. They have reached the end of the tunnel, but their path is blocked by a heavy iron grate that has rusted shut.

Trapped, the women nearly despair. Marguerite, however, notices that flooding has weakened the mortar around the stones holding the grate in place. They begin chipping away at the mortar with rocks until they manage to pry one of the large stones loose.

After removing a few more stones, the grate collapses into the water, clearing their path. They discover, however, that the opening leads directly into the swollen, treacherous Seine. Realizing they have no other choice, they resolve to swim. Marguerite goes first, successfully fighting the current to reach the far bank. Alouette and Sylvine then plunge into the freezing water to follow her.

The group realize their increased danger when they discover recent German survey marks, indicating the Nazis are exploring the area. After navigating a dangerously tight passage, they stop to rest in a former quarrymen’s lunchroom. Kristof observes the teenagers’ resilience and kindness toward one another.

Alesander is shaken by the German presence, feeling the weight of responsibility for the group’s safety. Kristof reassures him, affirming his trust. Sasha reveals that she has been building a mental map of their route, a “memory palace,” so they can retrace their steps if needed. Gérard compares her to the nymph Echo in the Metamorphoses, who used her limitations to save herself. Sasha recites a line of Latin from Ovid: “All things change, and we change with them” (383).

The group discovers an old monastery wine cellar partially hidden behind a collapsed wall. Alesander opens an ancient bottle of wine, and he, Kristof, and Ursula share a drink. To lighten the mood, Alesander introduces the Surrealist drawing game “Exquisite Corpse,” where each person draws a section of a body without seeing the other parts.

Kristof and Ursula are initially hesitant, but the teenagers enthusiastically join in. As Alesander predicted, the teens play without self-consciousness. The three adults create a strange hybrid creature: Alesander’s snake-headed Medusa contribution atop Ursula’s fluid, vaselike body and Kristof’s careful, almost mechanical legs. Alesander reflects on the human ability to create meaning from unseen fragments, relating it to the historical graffiti and masons’ marks on the tunnel walls left by those who sheltered there long ago.

After nearly 40 hours underground, time has lost its meaning for Sasha. The journey is disorienting but also filled with moments of unexpected beauty, such as quartz crystals and colorful bands in the stone. The stress of the journey causes friction, but the group’s bond deepens through acts of kindness and support.

Sasha finds herself thinking about Gérard, a welcome distraction from her fears about her family’s fate. She makes a pact with herself to hold her family in her mind without letting the worry consume her. Their journey continues until they reach a sinkhole in the tunnel floor. They must cross a narrow, crumbling ledge. The group makes it across one by one, anchored by a rope. Alesander is the last to cross, but the ledge beneath him gives way. Kristof is jerked forward and manages to brace himself, still holding the rope. The rope snaps and Alesander plummets into the darkness.

In 1664, Alouette, Marguerite, and Sylvine struggle onto the muddy bank of the Seine, just yards from Salpêtrière. They are dangerously exposed, so they find shelter in a nearby warehouse, where they discover dry workers’ clothes to replace their own.

Their respite is short-lived as guards with lanterns approach, searching the area. The three women hide a hayloft, pulling the ladder up after them. The guards enter and pass directly under their hiding spot. Convinced by false tracks leading away from the building, most of the guards leave to follow the trail. The remaining two soon give up their search, and the women are left alone in the darkness.

After the guards leave, the women escape the warehouse. With dawn approaching, they have little time to find sanctuary. They navigate through the dark, muddy streets. Reaching the Pont Marie, a bridge leading into the city, they find it blocked by guards questioning a ferryman.

Seeing several unattended skiffs moored nearby, they decide to steal one. They slip into a boat and push off into the powerful current of the Seine. They manage to row across the river, passing unnoticed under the bridge, and land on the right bank. Sylvine, who knows Paris, leads them through the maze-like streets of the Marais district. Just as the sky begins to lighten, they arrive at the convent of the Sisters of Saint Catherine and ring the bell, asking for sanctuary. A nun opens the door and lets them inside.

After Alesander falls, Kristof rappels into the sinkhole to rescue him. He finds Alesander severely injured. The group works together to haul Alesander back up to the tunnel, but his wounds are clearly fatal.

As he lies dying, Alesander speaks of his home in the Pyrenees. Kristof comforts him, and Annette hums a fragment of “Minor Swing” she has heard Alesander whistle throughout their journey. Before he dies, Alesander asks Kristof to promise that the path ahead is clear. After his death, Sasha writes in chalk on the tunnel wall a quote from the poet Horace, “Not all of me shall die,” (410) followed by a Latin invocation for the dead: ”Manes, remember him. Traveler, listen: He lived bravely” (410), with a drawing of a liberty bird. She explains the bird is a guide for the next traveler.

With Kristof leading them using Alesander’s maps, the group continues their journey. The loss of Alesander weighs heavily on them. Gérard and Sasha walk together, comforting each other with the hope that they will one day be reunited with their families.

After nearly 72 hours underground, they see a sliver of light. The tunnel opens into a meadow at dusk. In the distance, they see a low stone farmhouse: their first safe house. As they wait for full darkness, Sasha feels a sense of calm. She opens a new chamber in her memory palace, vowing to return after the war and search for her family. Taking Gérard’s hand, she steps forward into the unknown future.

After arriving at the convent, Alouette suffers a miscarriage. The nuns care for her with kindness and skill. The eldest sister asks if Alouette would like to name her son, and Alouette names him René, after her father; the sisters will bury him with prayers. The Mother Superior assures Alouette that they will use their influence in Paris to expose the abuses at Salpêtrière. She reveals that Alouette’s mother, Henriette, once took refuge at the same convent and is now living and working as an herbalist in Provins. She offers to write and tell Henriette that Alouette is safe. 

Days later, once they have recovered some strength, Alouette, Marguerite, and Sylvine leave the convent, hidden in a merchant’s cart. They travel west, toward Sylvine’s family home in Brittany, to begin a new life.

Nearly three months after escaping Paris, Sasha’s group is hiking through the hills south of Toulouse, nearing the Pyrenees and the Spanish border. Their group of refugees has grown, now including a family from Bruges and others who escaped persecution. Kristof tells Sasha that their route is becoming a well-traveled “corridor” or “chain” for people fleeing the Nazis.

They pause to rest, and Kristof reflects on their progress, saying that Alesander would be proud of them. Sasha agrees, feeling a mix of sadness and determination. The group continues their steady march south, united in their purpose as the afternoon light spreads across the valley.

In 1665, Étienne, having been contacted by the Sisters of Saint Catherine, travels toward Brittany in search of Alouette. He arrives at an inn in the town of Lamballe, just a few days’ journey from her supposed destination. He worries about how her ordeal at Salpêtrière may have changed her and is afraid to ask about her for fear of exposing her.

While eating in the common room, he is stunned to see Alouette enter. They reunite, and he explains how he found her. He delivers the news that her father died in prison and Alouette seems to have already known this in her heart. Étienne gives her the small limestone lark he carved for her; she traces its wings and murmurs their shared words, “Even stone can learn to fly” (429). He offers her his maps and help in escaping to Holland or England. She rests her head on his chest and takes his hand.

By 1666, Alouette, Étienne, Marguerite, and Sylvine have established a life in a small cottage on the cliffs of Brittany. Alouette, pregnant again, has spent the year creating a “color bible,” a collection of blue dye recipes gathered from local women, preserving their traditional knowledge.

As a storm begins, Alouette goes into labor. With the help of Étienne, Marguerite, and Étienne’s daughter Marie, she gives birth to a healthy baby girl, whom she names Christiane. When she begins to hemorrhage, Alouette realizes she is dying. Étienne holds her and their newborn daughter by the window. As she looks out at the dawn sky, she sees the perfect, unattainable shade of blue she has always sought. 

The narrative flashes forward, showing that Christiane will thrive, the other women will continue Alouette’s legacy of knowledge, and Étienne will ensure her “color bible” is preserved by the Sisters of Saint Catherine.

In 1857, a woman works in a small stained-glass studio in Paris. She is a distant descendant of Alouette, and she is using the unique blue dye formula that has been passed down through generations of women in her family. The recipe, a symbol of her ancestor’s creative genius and defiance, was never written down but passed orally from mother to daughter as an act of preservation and resistance.

The artist sees this special blue as the color of a lasting, transforming soul. After setting the last piece, she makes a small, hidden inscription in the glass. The completed panel, which depicts a skylark, is a vow to those who persevere through hardship. It is destined to endure through future revolutions and wars, its encoded history of female resilience unknown to future generations who will gaze upon it.