The Doctor, Romana, Adric and K9 encounter the enslaved time-sensitive Tharils, who lead them to a white void occupied only by the ruins of an old building and a spaceship - a dimension that might be the key to escaping E-Space.

• BBC
• Tom Baker
• Lalla Ward
• Matthew Waterhouse
• John Leeson
• Clifford Rose
• Kenneth Cope
• David Kincaid
• Freddie Earlle