Fermat's Room - Drawn together by a mysterious host, four mathematicians wind up locked in a shrinking room and bombarded by a series of tricky riddles. To avoid horrific deaths, the frantic scholars must quickly figure out the link that unites them all.
Created by Mark Gatiss, Steven Moffat. With Benedict Cumberbatch, Martin Freeman, Una Stubbs, Rupert Graves. A modern update finds the famous sleuth and his doctor partner solving crime in century London.