Red Cat by Peter Spiegelman

Growing up brothers John and David March detested one another; as adults their scorn for the other remains unabated. Thus John is more than shocked when his snobbish business executive David turns to him for help. The married David used an Internet site to arrange a tryst. The woman videotaped their performance, which if revealed would cost the older sibling his job and probably his wife; he wants his younger sibling, a private investigator to find out what is going on and how to prevent the personal disaster from occurring. The only additional clue is a red cat tattoo on the hooker.

John learns the female is Wren, who is not blackmailing David per say, but considers herself an artist selling her tapes of married men cheating with her to the highest bidding collector. The scenario takes a deadly spin when someone murders Wren. John assumes that a sex client committed the homicide, but wonders if righteous David could have performed the deed even as he ponders whether blood is thick enough to propel him to protect David especially if he turns out to be the killer.

Red Cat is a dark, brooding work, full of secrets, shame and desperation in even the most unexpected corners. John is terrific as he loathes his pompous "superior" older brother, but also resolves to do his best by him as he is family. Peter Spiegelman provides a great whodunit starring one of the best sleuths to hit the information age.