Using some well-placed clues provided by McSweeney, we set out for the secret island that held the vault. On arriving, we discovered someone by the name of Dr. M had already set up shop. From the looks of it, he'd been trying to crack the thing for years, growing steadily more frustrated in his failures and more paranoid as the decades rolled by. He'd built himself a fortress with security as tight as Fort Knox.
― Sly Cooper[src]
Kaine Island was an island in the southern Pacific Ocean, on which the Cooper Vault was located.
Many, if not all, members of the Cooper Clan after Slytunkhamen Cooper II traveled to Kaine Island at one point or another. Once they arrived, all of the Coopers, excluding Sly Cooper, set up their own shrine in the Cooper Vault in order to store their greatest treasures, including their canes.
For many years, Dr. M had tried to break into the Cooper Vault to retrieve the fortune for himself, but it proved impenetrable. Eventually, Sly arrived there and got into the Vault, using his cane as a key. He traveled throughout the Vault and discovered a new ability, the laser slide, from his father, Conner Cooper. After entering the inner sanctum, Dr. M followed him in, where they had a battle. The battle resulted in Sly getting hit by an electrical bolt fired from one of Dr. M's machines toward Inspector Carmelita Fox, which launched him into the rafters and seemingly gave him amnesia.
As the walls of the Vault began to crumble, thanks to Dr. M's machines, Sly and Carmelita escaped. The ceiling caved in, and presumably crushed Dr. M. An untouched part of the Vault was found by Sly, who left his cane and pouch behind to be found by Bentley and the rest of the Cooper Gang.
Later, Bentley and Penelope used their technology rebuild the Cooper Vault and make it more secure.
- The name, Kaine Island, is a pun on the Cooper family's famous canes.
- It is also the only name of an area in the game to not be said by any character.
- There's a well-known glitch were you can actually explore the island as Sly during "Beginning of the End," and with Carmelita during "Carmelita to the Rescue."