Something terrible has happened to Henry Knight; Sherlock and John investigate the truth about the monstrous creature which apparently killed their client's father. A hound from hell? What seems like fantasy in Baker Street is a very different prospect in the ultra-secret army base that looms over Dartmoor.
Elenco: Benedict Cumberbatch , Martin Freeman , Rupert Graves , Mark Gatiss , Una Stubbs , Amanda Abbington , Louise Brealey , Lars Mikkelsen , Mark Gatiss , Rupert Graves , Russell Tovey , Una Stubbs .