Bradley Headstone has heard that Eugene Wrayburn was indeed married in bed, and it seems as though he's going to get better. Now Headstone can't figure out why the police haven't come for him yet. He figures that maybe Eugene didn't identify him after all.
During one of Headstone's classes one day, Mr. Riderhood barges in and whispers to him that he knows about his whole scheme. Riderhood knows that Headstone arranged his clothing to look exactly like Riderhood's when he killed Eugene Wrayburn.
Riderhood also knows that Headstone intentionally cut his hand and shook blood over Riderhood's clothes to incriminate him further.
Riderhood invites Headstone back to his house at the river lock for a friendly chat. When Headstone gets there, Riderhood tells him that he (Riderhood) has all the evidence he needs to get Headstone convicted of trying to murder Eugene Wrayburn. And you know what that means...
... more blackmail!
Except this time around the blackmail doesn't last long. Headstone lunges at Riderhood and pulls him into the river lock. Riderhood isn't scared because he's certain a man can't drown once he's been revived from drowning before. But he's wrong, and both men die in the lock. Womp womp.