Returning from their adventure in medieval England, the Doctor and Sarah Jane are bewildered to find London deserted and under marshal law. Even more startling is the sudden appearance of a Tyrannosaurus Rex in the street. When they reach UNIT headquarters, they learn from the Brigadier that the city had to be evacuated when dinosaurs began appearing all over London. Fortunately, the prehistoric reptiles disappear almost as soon as they appear, but their random visits naturally caused considerable panic and some loss of life. The Doctor believes that the dinosaurs are being transported through time from the Mesozoic age, but he needs a live specimen to test his theory. Meanwhile, Sarah applies her reporter's instincts to uncovering a hidden agenda. This video features over two hours in color, but Episode 1 is in black-and-white.