Act One

London, 1909. In the Prologue, we learn the nature of the evening's bill of fare ("A Warning to the Audience"). In a prison cell, Monty Navaro, the ninth Earl of Highhurst, takes up a pen to write his memoir: "In the event of my execution, while I still have time." His story begins in a shabby flat in Clapham, where he receives an unexpected visit from Miss Shingle, an old friend of his recently departed mother ("You're a D'Ysquith").

With the stunning discovery that he is eighth in line to inherit a magnificent title and fortune, Monty sends a letter to the head of the family, Lord Asquith D'Ysquith, Sr., asking for a job in the D'Ysquith banking house. He then rushes to tell the news to his childhood sweetheart, Sibella Hallward, arriving just as she prepares to go out ("I Don't Know What I'd Do"). Monty tells her that only eight other D'Ysquiths stand before him in the line of succession, which means that he could be Earl himself some day. "And pigs might fly!" Sibella laughs. "Eight people would have to die for that to happen! How likely is that?!" Sibella teases Monty about her forthcoming outing with Lionel Holland, who is not only rich and good looking, but drives a motorcar. Regardless, Monty kisses her impulsively and passionately. Although Sibella shares his ardor, she draws the line at a future together. Sibella is determined above all else to marry a man with wealth and influence.

A letter from Asquith D'Ysquith, Jr., rebuffs any notion that Monty will be recognized by the D'Ysquiths ("Foolish to Think"). Among a group of tourists who are led by an informative guide, Monty visits Highhurst Castle, ancestral home of the D'Ysquiths, where the family portraits seem to speak directly to him ("A Warning to Monty"). The imposing and perpetually aggravated Earl, Lord Asquith D'Ysquith, discovers Monty on the wrong side of the velvet rope and ejects him ("I Don't Understand the Poor").

Seeking an ally, Monty visits the Reverend Lord Ezekial D'Ysquith. While enthusiastic about the architectural splendor of his historic church, the doddering cleric shows Monty no sympathy. In his zeal to share the view, Ezekial steps too close to the tower's edge. When he reaches out for help, Monty hesistates ("Foolish to Think – Reprise") and lets the Reverend fall. In one moment, Monty's life has changed forever... and, of course, the action has been set.

Monty then follows the man who snubbed him so unmercifully, Asquith D'Ysquith, Jr., to a winter resort, where he finds the young dandy skating on the lake with Miss Barley, his chorus-girl mistress ("Poison in My Pocket"). Grief-stricken over the "accidental" loss of his only son, Lord Asquith D'Ysquith, Sr., offers Monty a job at the family banking firm. Flush with excitement over his acceptance by the D'Ysquiths at last, Monty hurries to tell Sibella – only to learn that she is engaged to Lionel Holland ("Poor Monty").

At a village inn, Monty rescues wealthy landowner, Henry D'Ysquith, from the fists of an angry tenant farmer. Grateful, Henry buys Monty a round ("Better with a Man") and invites him back to his country estate, where he reveals his passion for beekeeping. Over time, he assures Monty that one builds up a resistance to bee stings: "I dare say it would take a hundred bees to kill me now." When Monty returns the following weekend to set a trap, he meets Henry's lovely, innocent sister, Phoebe D'Ysquith, with whom he develops an instant rapport. As the two draw closer, Phoebe is unaware that her brother is being pursued by a swarm of bees ("Inside Out"). Monty is left to console Phoebe, and it occurs to him that should he achieve his goal of becoming Earl, "I could find no finer woman to be my countess."

Lady Hyacinth D'Ysquith, an unmarried society matron of a certain age, is furious that her latest charitable venture has been ruined by scandal. She and her colleagues are aided in their search for a new cause by a helpful "Baron Philpot" aka Monty ("Lady Hyacinth Abroad"). After reading of Lady Hyacinth's tragic death at the hands of cannibals in deepest, darkest Africa, Lord Asquith D'Ysquith, Sr., notes Monty's closeness to the succession. While maintaining an affair with the newly wed Sibella, and continuing to offer consolation to the mourning Phoebe, Monty disposes of the fitness-obsessed Major Lord Bartholomew D'Ysquith and the transcendently terrible actress, Lady Salome D'Ysquith Pumphrey, whose Hedda Gabler takes naturalism one pistol shot too far. Asquith Sr.'s, sudden heart attack leaves only Lord Adalbert as the obstacle between Monty and the Earldom ("The Last One You'd Expect").

Act Two

At Asquith D'Ysquith, Sr.'s, funeral, the mourners discreetly ask the question on everyone's mind ("Why Are All the D'Ysquiths Dying?"). At Highhurst, Lord Adalbert is preoccupied with the same question ("Why Are All the D'Ysquiths Dying? – Reprise"). After an assignation with Sibella at his bachelor apartment, Monty explains why he stares at her so intently ("Sibella"). With the unexpected arrival of Phoebe, Sibella hides in the bedroom while Monty desperately tries to keep the two women apart ("I've Decided to Marry You"). Monty accepts Phoebe's proposal, with Sibella none the wiser.

To celebrate their engagement, Monty escorts Phoebe to a weekend with Lord Adalbert and his combative countess, Lady Eugenia, at Highhurst Castle ("Final Warning"), where he discovers the inconvenient presence of Sibella, also a weekend guest. At dinner, Monty is shocked to see Miss Shingle and learn that she has been a servant at Highhurst for 39 years. Monty realizes that this may be his only chance to complete his mission ("Poison in My Pocket – Reprise") but he is foiled in his attempt. With his relatives dropping like flies, Lord Adalbert relives his near-death experience in the Boer War ("Looking down the Barrel of a Gun") and collapses unexpectedly.

At the death of Lord Adalbert, Monty becomes the Ninth Earl of Highhurst. His triumph is short-lived, however, when, at his wedding to Phoebe, an Inspector from Scotland Yard arrests Monty for murder ("Stop! Wait! What?!"). At trial, Monty vehemently denies poisoning Lord Aldabert's port, but the circumstantial evidence is damning. Back in his prison cell on the eve of the verdict, Monty is astonished to discover that the unassuming janitor, Chauncey, is also a D'Ysquith. Phoebe visits Monty in his cell, and he tries his best to console her. She has but one question: "That woman, Mrs. Holland – is she in love with you?" Monty hesitates, which is all the answer that Phoebe needs.

That night, Sibella pays a surprise call on the Inspector while a Magistrate receives an unexpected visit from Phoebe ("That Horrible Woman"). With seemingly irrefutable evidence, the women each accuse the other of Lord Adalbert's murder, making it impossible for either of them – or Monty – to be charged. Monty is awakened by the news that he is being set free. As he emerges from prison, Monty is greeted by the secret conspirators, Sibella and Phoebe. Monty Navaro has finally triumphed at last... or has he? ("Finale")