Detective genius Nero Wolfe and his assistant, Archie Goodwin, are private investigators based in New York. With Wolfe's unmatchable wits and Archie's tireless legwork, no mystery is unsolvable. In this installment, Wolfe must prove the innocence of colleague Orrie Cather who is being charged with the murder of Isabel Kerr. As Archie deals with a colorful cast of characters, including Isabel's sister, brother-in-law, and benefactor, Wolfe uses mathematics and memory to crack this case.