The Gentleman's Guide to Vice and Virtue

The first book in Mackenzi Lee's Montague Siblings series is set in Europe during a period when young men of the English upper class customarily took a "Grand Tour" of the Continent's major cities to absorb culture before assuming adult responsibilities.

Henry "Monty" Montague, the eldest son of an English earl, wakes hungover beside his best friend, Percy Newton, on the morning they are to depart on their Tour. Monty narrates in first person, and his unspoken longing for Percy is clear: He would like to be sober the first time they are together, if that ever happens. Percy's late father brought him as an infant from Barbados, and Percy was raised by his white aunt and uncle in England after his father died. They have been inseparable since childhood.

Before the carriage leaves, Monty's father delivers a cold ultimatum: Any hint of Monty "mucking around with boys" will result in permanent disinheritance. The threat carries new weight because Monty's infant brother can now serve as an alternate heir. Monty departs with Percy, a tutor-guardian named Mr. Lockwood, and his 15-year-old sister Felicity, who is being delivered to a finishing school in Marseilles that she resents.

In Paris, Lockwood's relentless schedule leaves Monty bored. He and Percy escape to a music hall, where Percy composes a flirtatious limerick and Monty kisses him. The kiss escalates until Percy stops and asks if it is just a laugh. Terrified of exposing his true feelings, Monty deflects, and Percy pulls away with a quiet "Don't."

At a ball at the Palace of Versailles, Monty clashes with the Duke of Bourbon, the French king's recently dismissed prime minister, and retreats with a young Frenchwoman to the duke's private apartments. There he pockets an ebony trinket box with six alphabetical dials forming a combination lock. The duke walks in on them half-undressed, and Monty escapes through a window, ending up naked in the courtyard before the entire party. In the carriage home, Percy points out that a dark-skinned man in the same position would not have been allowed to simply walk away.

Lockwood declares the Tour over. On the road south, armed highwaymen ambush their carriage. Their leader, wearing a gold signet ring inscribed with the fleur-de-lis, the lily emblem of French royalty, demands the stolen box. The three fight back, flee into the forest, and Monty confesses to taking the box. That night, he accidentally reveals that his father beats him, a secret Felicity had never known.

After days of walking, they reach Marseilles, where Percy collapses in a violent seizure. Felicity takes charge while an apothecary named Pascal shelters them on his canal boat. Percy confesses he has epilepsy; no treatment has worked, and at the Tour's end he is being committed to a sanatorium. Monty is furious Percy kept this secret, but Percy says Monty has been too reckless to trust with the information. Felicity reveals she has secretly studied medicine for years, disguising textbooks inside romance-novel covers.

Pascal's grandmothers identify the object as a Baseggio puzzle box, a Venetian design meant to protect alchemical compounds, owned by Professor Mateu Robles, a once-prominent alchemist in the Spanish court known for his work on panaceas, or universal cure-alls. When the duke's soldiers come searching, Monty proposes they travel to Barcelona: If Robles studies cures, he might help Percy avoid the sanatorium. Monty secures funds from a bank and deliberately destroys a note that would reunite them with Lockwood, choosing the uncertain path to Spain.

In Barcelona, Helena Robles and her younger brother Dante accept the box but insist their father is dead. Monty discovers a letter sealed with the Bourbon crest referencing their father's "Lazarus Key," a mysterious object linked to the puzzle box, but Helena catches him and burns it. Research connects Robles's work to the biblical Lazarus, who was raised from the dead, and to a sinking island off Venice with a chapel named for Lazarus's sisters. At a gambling hall, Monty learns from the city prison warden that Mateu Robles is alive and imprisoned.

Under pressure, Dante confesses. His parents performed an alchemical experiment; his mother volunteered. The compound stopped her heart but left her suspended between life and death, her heart now a living panacea. Mateu hid her body in a tomb on the Venetian island before his arrest, and the Lazarus Key opens the vault. The island is sinking. Helena struck a deal with the duke to exchange the box for their father's freedom, but neither side can open it without the cipher only Mateu knows.

Monty gets himself arrested to meet Mateu in prison. Moved by Monty's sincerity, Mateu scratches six letters in the dust: the first notes of a song for the crystallophone, a glass instrument in the Robles house believed to summon the dead. Monty lies to the others, claiming Mateu refused to share the cipher, because he intends to retrieve the panacea for Percy without the siblings' knowledge. He opens the box in secret, hides the bone key in Percy's violin case, and when Helena discovers the empty box, she attacks him with a needle of belladonna, a toxic nightshade compound. Percy intervenes, and the three flee Barcelona.

A boatswain refuses to carry Percy because he is a free Black man, so the trio stows away on a merchant ship. In the cargo hold, Percy confesses that Monty's old love letters about another boy "wrecked" him; they are on the verge of kissing when cannonballs tear through the hull. Pirates board the vessel, and their captain, Scipio, takes them hostage. Scipio's crew are formerly enslaved sailors forced into piracy. Percy proposes a deal: His uncle on the Admiralty Court can issue legitimate letters of marque, or privateer licenses, far more valuable than ransom. Scipio agrees to transport them to Venice aboard his ship, the Eleftheria.

Weeks at sea transform the group. Percy thrives among crew members who share his skin color. Scipio teaches Monty to fight, and Monty declines a drink for the first time. In Venice during the Festa del Redentore, a Venetian religious festival, Monty and Percy share a passionate kiss. Percy proposes running away together, but Monty hesitates over their lack of money or prospects. Percy, stung, reveals he never wanted the panacea: He refuses to take another woman's life for his own health and does not believe he needs to be cured. Percy walks away.

Monty drinks himself into oblivion and is captured by the Duke of Bourbon, who holds him at gunpoint and sends Scipio with an ultimatum: Bring the key to the island at dawn, or Monty dies. Bourbon reveals that Monty's father secretly married a French woman before wedding Monty's mother, meaning the family's title and estate rest on a lie.

At dawn, Bourbon forces the group into bone-lined catacombs beneath the sinking island. Percy unlocks the vault, revealing Helena's mother suspended between life and death, her alchemical heart glowing beneath her skin. Bourbon forces Felicity to extract the heart, but when he demands Helena surrender it, she holds it toward the fire. Monty punches the duke, and Helena flings the heart into the flames. Bourbon fires his pistol beside Monty's head, clipping his right ear and burning the side of his face. The tunnels collapse, and Bourbon stays behind as the others flee. The Eleftheria rescues them as the island sinks beneath the lagoon.

The crew sails to Santorini, where Monty recovers. He has lost most of his right ear and the hearing on that side, with permanent scars. Scipio offers Felicity a position as ship's surgeon. On a sunlit beach, Monty tells Percy he wants to run away together, giving up his inheritance with no reservations. Percy confesses he loves Monty, and they kiss in the Aegean light. In a letter to his father, Monty declares he will not be coming home, choosing to walk away rather than expose the secret marriage. He and Percy intend to build a life together on their own terms.