Of all the missing Avengers episodes, this is the one about which the least is known. What IS known is that the gunshot that shatters the tank in the laboratory fight sequence was created through the use of a slingshot wielded by a technician. He was able to hit the test tube that was the intended target during rehearsal, but during the actual filming of the sequence, he panicked and hit the tank instead. This sequence was included in the Big Finish version.