In the Best Families

In the Best Families (British title "Even in the Best Families") is a Nero Wolfe detective novel by Rex Stout, first published by the Viking Press in 1950. The story was collected in the omnibus volumes "Five of a Kind" (Viking 1961) and "Triple Zeck" (Viking 1974).
This is the third of three Nero Wolfe books that involve crime boss Arnold Zeck and his widespread operations (the others are "And Be a Villain" and "The Second Confession"). In each book, Zeck – Wolfe's Moriarty – attempts to warn Wolfe off an investigation that Zeck believes will interfere with his criminal machinations. Each time, Wolfe refuses to cooperate, and there are consequences.
Plot introduction.
A wealthy wife hires Nero Wolfe to learn the source of her husband's mysterious income. In short order, Arnold Zeck horns in, the wife is murdered, and Wolfe disappears.
Plot summary.
Nero Wolfe is approached by heiress Sarah Rackham and her cousin Calvin Leeds, a breeder of Dobermans, to investigate Sarah's husband Barry, who maintains an unusually lavish lifestyle despite having no income or support from Sarah. After Wolfe reluctantly accepts the job, a tear-gas bomb disguised as a package of sausage is delivered to the brownstone the next day. Wolfe is warned to drop the case by Arnold Zeck, a shadowy criminal mastermind who has matched wits with him twice before. Although it is clear that Barry Rackham is one of Zeck's operatives, Wolfe orders Archie to investigate further.
Soon after Archie arrives at Sarah's estate, he discovers that she and her dog have been murdered. Archie calls Wolfe with the news and returns to the city, suspecting that Barry or someone else in Zeck's enterprise may be responsible. When he arrives, however, he discovers that Nero Wolfe has disappeared during the night, leaving only instructions that Archie should not look for him and a newspaper advertisement announcing Wolfe's retirement from the detective business. The Westchester authorities refuse to believe that Archie does not know where Wolfe is, and he is briefly detained as a material witness. While Archie is in jail, his cell-mate, Max Christy, implies that he is part of Zeck's organisation and offers Archie work.
After being released, Archie is hired by Sarah's daughter-in-law Annabel Frey to investigate her murder, but his attempts soon stall. Over the following months, as Wolfe seems unlikely to return, Archie opens his own detective agency. He is eventually approached by Christy, who renews his offer of employment in Zeck's organisation. Suspecting that Zeck is connected to Sarah's murder, Archie agrees. He is put in contact with Pete Roeder, a high-ranking operative in Zeck's organisation. During a private meeting, however, Roeder reveals he is in fact Wolfe, having lost weight and changed his appearance. After fleeing, Wolfe travelled to the West Coast and established his identity as Roeder to infiltrate Zeck's organisation in order to dismantle it from within, and now needs Archie's help to spring his trap. 
Archie persuades Lily Rowan to pose as Roeder's mistress so that the three of them can use her apartment as a covert meeting place. Zeck formally employs Archie to track down Barry, and Archie hires Saul Panzer, Fred Durkin, and Orrie Cather to do so. Barry soon realises what is happening and confronts Archie, but is terrified to learn that Zeck is also interested in his whereabouts; Barry had attempted to leave Zeck's employment, only to be threatened with exposure as a murderer. As Wolfe's trap nears completion, Archie is detained by the Westchester district attorney; Sarah's secretary Lina Darrow has formally claimed that Barry murdered his wife. Realising that Darrow's claims, although based on lies on her part, could get Barry convicted and thus ruin Wolfe's plan, Archie discredits Darrow by revealing that she was Barry's mistress and has been spurned by his refusal to marry her. 
Archie takes Barry to meet with Zeck to negotiate an end to his employment. During the meeting, Archie overpowers Zeck, and Wolfe reveals his true identity. Wolfe has gathered enough evidence to destroy Zeck's criminal empire, but is willing to trade it for an end to hostilities and the evidence Zeck has against Barry. Realising that he is doomed either way, Barry shoots Zeck with a concealed gun before being killed by Zeck's bodyguards. With Zeck dead, Wolfe returns to the brownstone intent on exposing Sarah's murderer. He summons the key witnesses to his office and reveals that Leeds, not Barry, killed Sarah. Leeds, who had raised and trained Sarah's dog, was the only person who could have gotten close enough to kill her and it without the dog raising an alarm or attacking. Barry had in fact committed an unrelated murder several years previously that Zeck had used to blackmail him. Afterwards, Archie takes a well-deserved vacation in Norway with Lily, where he receives a letter describing Wolfe's return to his normal routines — and informing him of Leeds' suicide in jail before the start of his trial.
The unfamiliar word.
In most Nero Wolfe novels and novellas, there is at least one unfamiliar word, usually spoken by Wolfe. "In the Best Families" contains the following:
Adaptations.
"Nero Wolfe" (Paramount Television).
"In the Best Families" was adapted as the seventh episode of "Nero Wolfe" (1981), an NBC TV series starring William Conrad as Nero Wolfe and Lee Horsley as Archie Goodwin. Other members of the regular cast include George Voskovec (Fritz Brenner), Robert Coote (Theodore Horstmann), George Wyner (Saul Panzer) and Allan Miller (Inspector Cramer). Guest stars include Linden Chiles (Calvin Leeds), Juanin Clay (Annabel Frey), Lawrence Casey (Barry Rackham), Burr DeBenning (Max Christy), Diana Douglas (Sarah Rackham), Robert Loggia (Arnold Dorso [Zeck]) and Alex Rodine (Marko Vukcic). Directed by George McCowan from a teleplay by Alfred Hayes, "In the Best Families" aired March 6, 1981.