Malbenia was a technician who volunteered to participate in an experiment with the copy of the First Doctor's mind. Steven Taylor described him as "a good kid, but no one important".
The experiment was an attempt to see if the copy could transfer its mind out of the jar and into another body. It lied to Malbenia, telling him that the process was not dangerous and could be easily reversed. This was not true as during the experiment Malbenia's mind was overwritten with the copy's. Due to an error, Malbenia's brain was fried, forcing the copy to return to it's jar.