Audio problem: When Culp is walking from his boat to the window outside the laboratory, some dialogue from Dr Orchard describing the theramine process can be heard in the background. When we are in the laboratory, Dr Orchard describes the process with the same dialogue soundtrack.
Continuity mistake: When we first see Virgil in the cockpit of Thunderbird 2 in the launch sequence at Tracy Island, he has nothing on his head. Later on, when we see both him and Brains, Virgil is now wearing his International Rescue hat, but when we see Virgil after the launch, the hat has gone.
Continuity mistake: When the tied up Penelope initially attempts to contact Jeff, you can see two books to the left of the bomb standing up. But when she tries to contact Jeff from the centre of the room, the books have suddenly been knocked over. In the next shot of Penelope the books are standing up again.