Who leaves a wedding early? In The Sign of Three, it's the best man, namely Sherlock (Benedict Cumberbatch). John Watson (Martin Freeman) may live to regret offering the role to a man who didn't realize he was John's best friend, but more importantly, one of the guests at John's wedding to Mary Morstan (Amanda Abbington) may not live to see the end of the day.
Too bad that Sherlock is unable to focus his tremendous powers of deduction on the murder that's hatching right under his nose, but then the responsibilities of a best man are more diabolically exhausting than preventing a very clever killing.
