Heart Of New York
A pair of safe crackers break into a Spectrum Security vault, expecting to find millions of dollars. Instead they are foiled when they discover reports that are class 'A' security - top secret.
However, when they read through their catch, they discover the Mysterons' powers of retrometabolism, and decide they can use it to their advantage. Faking their own deaths in full view of a watch tower, they pass themselves off as Mysterons in order to get to New York and into the centre without suspicion.
When they reach their destination, the Second Bank of America, Captain Black locks them in the safe and blows up the bank with them trapped inside.
A neat bit of poetic justice, I thought. The Mysterons had more morals than the humans when it came to greed!