Published in the TV Century 21 magazine #1-11, January 23 - April 3, 1965. Reprinted in Action 21 in 1988 and Thunderbirds The Comic in 1991.
In addition to introducing both Lady Penelope and her butler/chauffeur/assistant 'Nosey' Parker and explaining how they met, this adventure shows the first run-in with her archenemy, Mr. Steelman. Lady Penelope recruits Parker to help break into a safe at a foreign embassy to destroy plans for a hydromic device capable of destroying the world. This turns into a rescue mission trying to save one of the Lady's operatives and pits her against the rich man wanting to be the richest man, Mr. Steelman.