Nigel tries to tell Reggie about a letter they have received and how it's imperative that they do something about it. Reggie is dismissive, Nigel does a bunk to L.A., where the letter-writer lives, Reggie's girlfriend, Laura, is aloof, the body of Reggie's nasty clerk is found in Nigel's office, another body is discovered in L.A., and Nigel is suspected of murder on two continents.
Nigel barely appears in the book, which is a pity because he appears to be the more interesting of the two brothers. Perhaps the second book, The Brothers of Baker Street, fulfills the promise of such a creative idea, but this one meanders a bit and spends far too much time in Los Angeles. Also, there's an unnecessary complication with the vaguely characterized girlfriend. Sherlock Holmes means England, not Beverly Hills!
However, here's another pat on the author's back for another great idea: The letter in question was written 20 years ago by a young girl worried about her father. Nigel has received another letter from the now-grown woman wanting the original enclosures back. This was such a sweet idea that a young girl would write to her hero, Sherlock Holmes, to request his help. Robertson definitely is worth another look.