"Failure Five" is a robot made from scraps by a low-level government scientist which has gained intelligence and wants to steal Machine Man's body. This leads to first the kidnapping of MM's friend Peter Spalding and then a confrontation between the two robots (with MM series regular Colonel Krag also showing up).
It feels like Ditko might have had something else planned for this story that didn't make it into the script. The art, however, is really nice. Cockrum was a really good fit for Ditko (I think this is the only time Cockrum inked Ditko), the robot villain design is nicely wacky and the mixture of that and MM's stretching arms makes for some good stuff in the fight scenes.