Nuclear device (The Man from MI.5)

The plans to a nuclear device were created by a scientist living in an undisclosed location.

History
The plans to the device were originally created by a scientist living in an undisclosed location, before being given to MI5 agent Captain Blacker, who kept them in a black cylindrical container aboard his yacht in January 1965. While waiting for fellow agent Jimmy Bondson to arrive to "rendezvous" (later described as a "good cover" by Bondson) with him, criminal gang leader Carl snuck aboard the yacht and shot Blacker 5 times with a Henrietta .45 Supermatic. He then proceeded to rifle through his documents before finding the plans, which he proceeded to take with him. Carl then proceeded to blow up the ship with an explosive. This explosion was seen by MI5 agents Tidman and Jimmy Bondson, who were just arriving in a boat. Bondson ultimately decided to don a diving suit, and searched the wrecked ship for the plans. After finding no plans and the corpse of Blacker, he returned, and decided to contact International Rescue for help stopping the criminals and recovering the plans. Through this, a discussion was had between him and Lady Penelope Creighton-Ward at midnight in the Forest of Digne regarding the risk of the plans "[falling] into the wrong hands", that being world-threatening danger, as well as the vitality of the plans and why he needed the help of International Rescue, that being because they "[had] the most advanced equipment in the world", and "millions of lives" depended on it. Ultimately, International Rescue agreed to help.

Later, the plans were being stored aboard the submarine occupied by Carl's gang. After Gordon Tracy shot a harpoon from Thunderbird 4 which drilled into the sub and released a gas which put the criminals to sleep, Gordon got on board and recovered the plans, saying that they "look[ed] intact", and that Penelope could "put Bondson's mind at rest". In another scheduled meetup in the Forest of Digne, Lady Penelope used a speaker system to communicate with Bondson, ordering him to walk to the large tree at the edge of the clearing. Here, the plans had been placed within his reach, so he picked them up, and was ordered to return to his car. (TV: The Man from MI.5)