Franklin wakes up the morning after the experiment to find himself in Rachel's sitting room, being watched by Rachel herself.
They do some smooching, and then go down to breakfast.
Franklin goes back to London with Mr. Bruff – they need to be in town in case the diamond is redeemed from the bank.
They arrive at the bank.
Mr. Bruff has left a clever little boy, who is nicknamed "Gooseberry," to watch outside the bank.
No one expects to be spied on by a kid, so Gooseberry is the perfect person to have on watch.
They go into the bank with Gooseberry.
Two other people are stationed in the bank.
One of them tells Mr. Bruff that a tall man with a dark complexion in a sailor's uniform had gone into the bank, but that there was no sign of the three Indians.
Then they see Mr. Luker go in.
They figure that Mr. Luker will pass the diamond to someone secretly, and, if they keep their eyes open, they'll see who it is.
They see Mr. Luker pass a man in a grey suit, and they figure he's the one.
Bruff and Franklin follow the man carefully through the street, because Gooseberry has already disappeared.
It turns out the man in grey is just a businessman, so they followed the wrong guy!
But they figure Gooseberry probably saw what really happened and followed the right person.
They don't see Gooseberry again until the following morning.
Sergeant Cuff arrives at the same time as Gooseberry, so he takes charge of questioning the boy.
The detective is very impressed with Gooseberry's talents as a spy.
Gooseberry says that he saw Mr. Luker pass something to the tall, dark man dressed as a sailor, so he followed when the man left.
Mr. Bruff sends a note, which arrives just then, to say that he's very sick and can't leave his house that day.
Franklin sends a note back to say that Cuff has arrived, and then goes back to hear the rest of Gooseberry's story:
Gooseberry had followed the man with the black beard in the sailor's uniform to the Tower Wharf (on the east end of London, by the River Thames).
The man had asked to go on board a ship, but was told that no one could board until the next morning.
The boy noticed another man waiting and eavesdropping on the sailor.
The other man was dressed as a mechanic, and Gooseberry saw the mechanic speak to a different man in a cab – the man in the cab looked like an Indian.
So probably the mechanic is a spy, hired by the three Indians to follow the Moonstone.
The sailor took a room at a public house (what we'd now call a motel) called the "Wheel of Fortune."
Gooseberry was able to follow the sailor without being noticed, because he's just a kid.
Then Gooseberry saw the mechanic go into the public house, too – and then, a little while later, he heard angry voices, and then saw the mechanic get booted out of the public house for being drunk and going into the wrong bedroom while insisting that it was his.
The mechanic reeled around like a drunk until he got to a side street, and then he mysteriously sobered up and walked like a normal person.
Sergeant Cuff realizes that the mechanic must have been trying to figure out which room the sailor had taken, and he succeeded – Gooseberry heard the owners of the public house mention that the occupant of Number Ten had been disturbed.
That means that the Indians must know exactly where the Moonstone was last night!
So Cuff and Franklin take a cab to the "Wheel of Fortune" immediately.
When they arrive, the landlord tells them that the sailor in Number Ten was supposed to have gotten a wake-up call at 7am, but he never got up or answered the door – and the door is locked from the inside.
The landlord says that Number Ten has a trapdoor leading up to the roof. He's afraid that the sailor snuck out during the night to avoid paying for his room.
A carpenter arrives to break down the door.
When they get in, they see the sailor in the bed, with a pillow over his face.
Cuff tells them that the sailor is dead, so they should call for the police and for a doctor.
The sailor has been smothered.
Gooseberry is with them, and notices an empty box with a receipt from the bank – so this was the man who had redeemed the Moonstone from the bank and picked it up from Luker the day before!
Cuff notices that the sailor is not really dark complexioned – he has makeup on his face.
Cuff wipes the dead man's face clean and pulls off the fake beard.