In Los Angeles, a geological surveyor maps out a proposed subway route—and then goes missing. His eight-year-old daughter in her desperation turns to the one person she thinks might help—she writes a letter to Sherlock Holmes. That letter creates an uproar at 221b Baker Street, which now houses the law offices of attorney and man about town Reggie Heath and his hapless brother Nigel. Instead of filing the letter like he's supposed to, Nigel decides to investigate. Soon he's flying off to L.A., inconsiderately leaving a very dead body on the floor in his office. Big brother Reggie follows Nigel to California, as does Reggie's sometime lover, Laura – a quick-witted stage actress who's captured the hearts of both brothers. When Nigel is arrested, Reggie must use all his wits to solve a case that Sherlock Holmes would have savored, and Sir Arthur Conan Doyle fans will adore.