SEASON FINALE: Last week’s episode, Sign of Three, was a mostly comic departure for Sherlock, but you have to admit, the last-second reveal that added new meaning to its title – a play on Sir Arthur Conan Doyle’s original Sign of Four Sherlock Holmes mystery – was as clever as it was unexpected. Tonight, the third and final story in Season 3 of Sherlock is presented. It’s His Last Vow, and introduces a new criminal mastermind for Holmes to confront: a media mogul named Charles Augustus Magnusson, played by Lars Mikkelsen, of Borgen and the original version of The Killing. Benedict Cumberbatch, Martin Freeman star. Check local listings.