Richard Cobb was the spoiled and cold-hearted cousin of Geoffrey and Michael Radcliffe, who helped them run Radcliffe Colliery and had his sights set on stealing away both the mining company and Geoffery's fiancee Helen Manson. In order to do both Richard killed Michael by bashing him over the head with a wrench and framed Geoffrey for the crime with the help of Willie Spears.
He then feigned sympathy for his condemned cousin's plight, little knowing that family friend Dr. Frank Griffin helped him escape from prison using Dr. Jack Griffin's invisibility formula. Soon Geoffrey found out that it was Richard who had killed Michael and came after him for revenge. Richard escaped and sought police protection with Inspector Sampson, but that didn't save him for long.
Geoffrey used Richard's own gun to force his wicked cousin to come with him back to colliery, where he also had Willie Spears held captive. Richard killed Spears after learning that it was he who had exposed him to Geoffrey, then threw out the lights so that he became as invisible to Geoffery as Geoffrey was to him. The two tussled in the dark, but eventually Richard escaped and ran to the coal dumps.
Geoffrey pursued, and despite the interferance of Inspector Sampson's plain-clothes detectives and several concerned miners, caught up to Richard and the two resumed fighting atop a coal cart which was getting ready to dump its load off the conveyor belt. Sampson shot Geoffrey from below, stopping him from killing Richard even as he tried to force Richard to confess to everyone that he had killed Michael.
Richard's reprieve was short-lived. The coal cart dumped its load before he had a chance to get out, and not only did Richard plummet about fifty feet, but he ended up buried alive under a ton of coal. Although he was pulled from the rubble, his wounds were fatal. Seemingly remorseful about what he had dobne, he confessed his crime to Helen before perishing.