Professor Keller has created a machine that can pacify even the most dangerous of criminals. But when the Doctor and Jo arrive at Stangmoor Prison for a demonstration, things start to go horribly wrong – especially when they discover that the Doctor’s old enemy Master is responsible for the machine. What could he possibly want from the criminals? And what connects him with an impending World Peace Conference? Special Features: • Commentary with actors Katy Manning (Jo Grant), Pik-Sen Lim (Chin Lee) and Fernanda Marlowe (Corporal Bell), director Timothy Combe, producer Barry Letts, script editor Terrance Dicks and stunt arranger Derek Ware. Moderated by Toby Hadoke. • The Military Mind - A look at the making of the story. Featuring actors Nicholas Courtney, Pik-Sen Lim and Fernanda Marlow, director Timothy Combe, producer Barry Letts and script editor Terrance Dicks. • Now and Then - The latest in our long-running series visits the filming locations used in the story to see how they have changed over the years. • Behind the Scenes: Television Centre Back in 1971, presenter Norman Tozer visited BBC Television Centre to find out what went on over 24 hours in the life of what was then an incredibly busy ‘television factory’. • Radio Times listings (DVD-ROM) • 1971 Kellogg’s Sugar Smacks promotion (DVD-ROM) • Programme subtitles • Production information subtitles • Photo gallery • Coming soon trailer • Digitally remastered picture and sound quality