San Francisco Kills — Denny Martin Flinn

...if there is any here present who knows any just cause why they may not lawfully be joined in marriage, I require him now to make it known... Following the priest's request, a shot rang out and the groom fell dead.
What kind of killer was clever enough to get away with murder in front of hundreds of witnesses? That is just the sort of question that appeals to Spencer Holmes, a San Francisco detective who has inherited a fascination for foul play, a talent for deduction, good looks, and hoards of money from his illustrious grandfather, the immortal super sleuth Sherlock Holmes.
In a case as complicated as they come. Spencer Holmes, assisted by his inscrutable companion Sowhat Dihje, must use his formidable intelligence to follow a faint trail that leads from the mansions of the well-to-do into the not-so-distant past - to ferret out a remarkable affair of friendship, love...and murder.