In New York City's Bowery neighborhood, lawyer J. Ellison Higby gives Horace Debussy "Sach" Jones a letter in which Sach is identified as a potential heir to the estate of Sir Percy, Earl of Walsingham in England. The letter includes a first-class ticket for Sach to travel on a luxury steamship. Sach's friend, Terence Aloysius "Slip" Mahoney, believes that Sach will need the support of his friends in England, and proposes trading in the ticket for four lower-class tickets for himself, and their friends, Butch Williams and Chuck Anderson. When Louie Dumbrowski, the elderly owner of the sweets shop where the boys meet, attends a farewell party in the boys's cabin and is accidentally locked in the closet, the ship leaves port with Louie as an unwitting stowaway. After witnessing the captain's cruel treatment of another stowaway, the boys keep Louie's presence a secret, and Slip orders Sach to spend the remainder of the trip in a steamer trunk so that it will appear there are only four residents in their cabin. Upon arriving in London, Sach proves it was time well spent, by impressing his friends with his copious knowledge of London history, learned from reading a guidebook while he was trapped in the trunk. At Walsingham Castle, meanwhile, Sach's fellow heirs, Sir Edgar Whipsnade, Lady Agatha, Sir Reggie, Sir Herbert and Lady Marcia, are plotting to rid themselves of Sach, whom they perceive as yet another competitor for Sir Percy's fortune. Sir Percy, however, warmly greets the Americans upon their arrival. Confined to a wheelchair, Sir Percy believes he is dying and announces that he hopes to get to know all his potential heirs and thereby make a fair division of his estate. The Britons hope that Sach's uncouth American manners will soon put him out of Sir Percy's favor, but Sach's good nature impresses and invigorates the elderly man. The British heirs then plot to kill Sach after he convinces Sir Percy to discontinue taking his medicine and to eat for pleasure. Both Sach and Sir Percy are unaware that the medicine is actually making him ill, as his relatives had planned, rather than making him well. Working in collusion with the heirs, the butler Hoskins leads Sach and Slip to their rooms, and then frightens them with ghost stories. That night, Sach's fears are realized when a hooded figure with a hatchet attempts to kill him. After Sach is knocked unconscious by a helmet he had positioned over the bedroom door to stop an intruder, the hooded figure, actually Herbert in disguise, escapes. The next morning, Sach appears to have been invigorated by his deep sleep. Sir Percy's health continues to improve, and, no longer needing the wheelchair, he hosts a party to introduce his American guests. The next day, Sir Percy thanks Sach for his kindness and informs him of his plan to correct a two-hundred-year old injustice wrought by Sir Percy's ancestor, Sir Charles, against Sach's ancestor. Sir Percy recalls that the event occurred in the same chamber in which they now stand: Sir Charles had accused Sir Horace Debussy Jones and his friends of passing worthless I.O.U.s at an inn, and banished them to Manhattan in New Amsterdam. The friends were angry that they were being exiled to the colonies but were powerless against Sir Charles. Having recounted the story, Sir Percy now appoints Sach as his principal heir. Sach goes to tell his friends the good news but is distracted by Marcia, who seduces him into revealing his secret. Marcia and the other heirs then decide to kill Sir Percy before he can alter his current will. Slip, meanwhile, realizes that Sach's indiscretion has put Sir Percy in danger, and so the friends split up to search for the earl, who has disappeared. Unable to locate Sir Percy, Herbert and Reggie attempt to kill Sach, but he eludes them and stumbles into a torture chamber. Several more attempts are made on Sach's life until someone mysteriously knocks out both Reggie and Herbert. After Edgar appears and holds Sach and Slip, who has come to help his friend, at gunpoint, the mysterious assailant emerges and is revealed to be Sir Percy. Hoskins enters the dungeon and asks Edgar's permission to shoot the men, but when he is given the gun, he proves his loyalty to Sir Percy by turning the weapon on Edgar, Herbert and Reggie. A swordfight erupts between the men while upstairs, Marcia and Agatha lock Butch and Chuck in a room. Detective Ames of Scotland Yard arrives with the police, having been summoned earlier by Hoskins, and they arrest the women and free Butch and Chuck, who then lead them to the dungeon. There they find that Edgar, Herbert and Reggie are securely locked up in the stocks, and that everyone else is safe. Lawyer Higby arrives unexpectedly and announces that he mistakenly identified Sach as Sir Percy's relative, but that the true heir lives in Australia. As if this news was not painful enough, Sach is accidentally knocked unconscious by several cannonballs that slip out of their mounts. Sir Percy later congratulates a bandaged Sach for maintaining his dignity in the face of the bad news. When Sach expresses his regret that he never got to go on a fox hunt, Sir Percy informs him that there have been no foxes in the area for hundreds of years. Moments later, a fox chased by beagles runs through the room and both Sach and Sir Percy heed the call of the hunt.
