Nick Moran as Christie Malry is a twenty-something in West London who lives with his terminally ill mother and works in a dull office, a routine he tolerates only by letting his imagination drift into violent fantasies, including visions of threatening his manager with a shotgun. At his friend Bernie’s suggestion, he enrolls in a night class in accountancy, where he encounters the ideas of Fra Luca Pacioli and the principle of double-entry bookkeeping, notably detailed in the work Summa de arithmetica. Christie soon resigns from his job, only to endure the shock of Bernie’s sudden death in a vehicle collision.
Interwoven with the main thread are Renaissance Milan scenes in which Fra Luca Pacioli teaches his theories on accounting at the court of Ludovico Sforza. In this backdrop, Leonardo da Vinci, Mattia Sbragia as Leonardo, contends with Church interference as he faces an imminent invasion by the French army, highlighting a tension between artistic vision and institutional control.
Back in London, Christie grows more enthralled with the idea that debits must be balanced by credits, and he begins to wonder whether the same rule could apply to his own life—pondering who will credit him for his mother’s illness. He takes a job at Tapper’s chocolate factory, where he meets Headlam, an eccentric co-worker played by Neil Stuke, and starts recording perceived wrongs in a ledger he carries with him, explaining his system to his mother moments before she dies.
Christie’s early attempts at balancing wrongs skew toward petty acts of vandalism and mischief: he keys a car after it horned him, he hurls a brick through the window of an off-license he suspects sold bootleg alcohol, and he sabotages his employer by discarding letters of complaint. He also begins a relationship with Carol, Kate Ashfield as Carol, whom he meets at the local butcher’s shop. Yet as the ledger grows heavier, his revenge becomes more serious, drawing him toward calculated violence and even terrorism, guided by references like The Anarchist Cookbook.
The scale of Christie’s actions expands to dramatic levels: he phones the police to claim he planted a bomb in Leicester Square; after the Foreign Secretary dies of a heart attack, he makes another call claiming responsibility. The government, unsure of the true culprit, blames Iraq and escalates military action abroad. Christie’s methods move from acts of vandalism to inflicting real damage, including placing a home-made bomb inside a toy train to blow up a tax office. He then poisons a reservoir in West London, a catastrophe that is attributed to Iraq and triggers air strikes against the country.
Meanwhile, in the personal sphere, Carol learns that Christie is hospitalized after a bus bombing, and she mournfully realizes that his vigilant ledger contains extensive plans to bomb the Houses of Parliament. The final turn of events reveals that Christie’s bomb was meant for Parliament, but it detonates prematurely as the bus crosses Westminster Bridge, leaving Carol by his side as he dies in hospital.
Across the Renaissance threads, figures like Salai and Giacomo—Francesco Giuffrida and Salvatore Lazzaro—appear within Leonardo’s orbit, underscoring themes of ambition, invention, and the cost of pursuing one’s own truths. The film blends Christie’s modern arithmetic of grievance with the ancient arithmetic of art and power, drawing a stark through-line between accounting as a system of credits and debits and the human reckonings that follow when life itself becomes a ledger.
