The time is 1836; the place is Istanbul. A series of bizarre grisly murders have thrown the city into a panic. The Sultan and his personal protector, the Seraskier, have ordered Yashim Togalu - a strangely enigmatic eunuch – to try to solve the riddle of these terrible crimes.

For Yashim, time is of the essence. He has just ten days before the Sultan embarks on a great Review designed to show how he is head of the New Guard, an efficient and reformed army heavily modeled on Western soldiers. In existence for only ten years, The New Guard are not as strong as they could be - a succession of foreign instructors, the "ferenghi" from Europe, have not yet put them through their paces. Young, ambitious, and undoubtedly officers of good family, the murder victims were members of this guard.

Yashim - who can furtively sneak through the City's squalid back alleyways just as readily as slinking around the lavish Topkapi Palace – is also asked to investigate the mysterious strangling of a young girl of the Sultan's harem, the discovery of which rocks the very foundations of the Palace.

The Ottoman Empire is seen to be embarking on a period of enormous and profound change. The Sultan is a born modernizer who seeks to merge his realm with European values and traditions, intent to promote quality of people under a single law and employ Western-style ministers instead of the "pasha."

Yashim soon discovers that evidence of the murders points towards a newly revitalized Janissary Corps. Embittered at what they see as the loss of the Empire and wary of modernism, the Janissaries were brutally suppressed ten years ago. Many were killed but others escaped, clinging stubbornly to the traditions of their forefathers, contemptuous of innovation, and intent on holding this newly reinvigorated Empire to ransom. Once the Ottoman Empire's crack troops, the Janissaries have now degenerated - or evolved – into an armed mafia, terrorizing the sultans, fire razing, thieving and exhorting with impunity.

Yashim's investigation is measured yet rigorous and riddled with clues as baffling and intricate as Istanbul's impenetrable alleys. The Janissaries seem to want blood. Perhaps the murders are a prelude to death in the streets, where men are torn apart and made the sacrifice of princes. Yashim is thwarted at every turn by the complexities of the current political climate and by the constraints of a society with rigid standards, where passion and faith is too free and too dangerous for the true believers.

Spurred on by the growing spirit of rebellion, openly fostered by the Russians, Istanbul is quietly festering, threatening to collapse under the weight of corruption, payoffs and external political forces. The rot is decaying side by side – "in one ear, dereliction whispers of opportunity, and in another ear, delinquency and corruption." Author Jason Goodwin excels at recreating the sights, sounds and smells, bringing to life this exotic and mysterious city. It's a place of mosques, churches, and synagogues, of markets and emporia, of tradesmen, soldiers and beggars, the jumble of roofs and minarets and domes, "the city to beat all cities, overcrowded and greedy."

As Yashim gets ever closer to the perpetrators, he must navigate myriad-crooked streets and twining alleyways, and he begins to realize the Janissaries have for centuries been the voices of the people, the beating heart and the absolute soul of the empire. In this world, kinship is combined with much that is already ragged and moldering in the ancient metropolis.

From the cracked basilicas to the sagging wooden houses, from the office of the patriarch to waterlogged pilings in the back alleys of the old town by the Golden Horn, The Janissary Tree is a compelling and beautifully written account on an Empire on the edge as it struggles with the inexorableness of change and transformation.