Sherlock and Joan assist Detective Bell in the investigation into the shooting death of an amateur superhero who went by the name Midnight Ranger. He acted out the character to the point where he was actually fighting crime. Superlative Comics, the company behind the original Midnight Ranger, denies knowing the identity of this flesh-and-blood version.

One of Midnight Ranger's fellow superheroes, The Standard-Bearer, approaches Sherlock and gives him their victim's real name, Mike Stratton. Visiting Stratton's residence, they learn that Al Baxter, the editor from Superlative, knew full well who he was.

Baxter claims that they were friends, and Stratton had his blessing to wear the costume. Baxter was the grandson of the person who originally created Midnight Ranger.

Further investigation reveals that Baxter had a drinking problem and was incredibly bitter about the way Superlative treated his grandfather. In fact, he was planning a workplace massacre that night, but Stratton, suspecting something, intercepted him, only to get shot himself. Baxter confesses everything after Sherlock confronts him.

Meanwhile, Morland wants to hire Joan to discover a mole in his office, who messed up a major business deal. Joan later tells Morland that there was no mole, but later confronts the mole and blackmails him into being a mole for her in Morland's office.