The inspector, Eugene, Mortimer, and Riderhood row up to Gaffer's boat, which has gotten lodged between two large ships on the bank of the river. Riderhood hops into Gaffer's boat and notices that there's a rope hanging into the water. He tugs on the rope and finds that it's tight; whatever it's tied to must be heavy.
It's not easy pulling up the rope because of the way the boat is positioned. But eventually, the inspector is able to haul in whatever is attached to the other end. They haul it onto the shore and realize that it's the body of Gaffer Hexam, who's been dead for some time now. Gross.
It looks like Hexam got himself tangled in some rope that he would normally use to fish a dead body out of the river. The more he struggled, the more the rope tightened around him… until he drowned.
The inspector says that he'll go tell Lizzie Hexam about what has happened. Meanwhile, Mortimer and Eugene are so tired that they head back to their office and pass out.
The next morning, Mortimer realizes that Eugene "took a walk" after he (Mortimer) passed out. But we don't quite know why Eugene did this or where he went.