This is it, Sly, the gang's assembled and are in position to help you get up to that vault. For the rest of the operation, you are "the ball."
― Mission briefing[src]
Sly infiltrated the island's outskirts, taking out three elephant mutant guards in the process. After making his way to a small section of the island, Bentley briefed him on the mission, making sure that the rest of the gang was in sync.[note 1] Afterward, Sly made his way further into the island, until he was obstructed by several guards on support beams blocking his path along a ledge. In response, Agent Heartthrob used a Yank 86 to clear the way.
Not long after, Sly came to a gap that was too large to jump across. Agent Old Rock was deployed to knock down a nearby satellite tower, that way Sly could Rail Walk across. Soon after, Sly came across an air vent that directly led to the ceiling of Dr. M's underground lab. He called in Agent Monarch to launch a firework at the vent to bust it wide open, allowing Sly to enter. Once inside, Agent Deep-Six used his harpoon gun to destroy two forcefields blocking Sly's path, causing water from outside to leak into the lab.
As Sly made his way to the top of the lab elevator, Dr. M and a henchman named Richards entered the lab and approached the elevator. Dr. M and Richards started a seemingly harmless conversation, with the former asking Richards how his family was doing. With Sly standing on top of the elevator, just above Dr. M and Richards, the elevator began to rise to the surface. On the ride up, Dr. M told Richards that he would not be seeing his family again, as M poisoned his drink during the lunch break. Dr. M explained to Richards his intolerance of poor performance, for the latter forgot to change the code for a newly-installed security system from the default "1-2-3." A terrified Richards promised to do better, but Dr. M warned him he was seconds from death, at which point he tumbled over and died. Just as the elevator reached the surface, Dr. M then received a call about water leaking into the lab, and headed back down the elevator to investigate, while also requesting a janitor to clean up after Richards. Sly jumped off the elevator just before it went back down and its shaft closed, so that he could continue his approach to the Cooper Vault.
Bentley told Sly that he was on his way to meet Sly at the vault for the hauling of the vault's loot. Sly made his way across several wires towards the vault, but accidentally set off the alarm in the process, causing turrets to open fire on him. He reached the security system and inputted the 1-2-3 code, causing the vault's security to deactivate. Sly inserted his cane into the vault lock, and the vault proceeded to open. Just before the vault could open all the way, a missile struck the vault door, knocking Sly away and shutting the vault again. The shooter was revealed to be none other than Dr. M himself, flying a jetpack. After a brief confrontation, Bentley snuck up behind the doctor and fired a sleep dart at him, disorienting him long enough for Sly and Bentley to attempt their escape. However, just before reaching their ship, Dr. M appeared with a giant mutant primate under his control, and captured Bentley. Sly saved his friend by tossing his cane into the mouth of the monster, causing it to release Bentley. However, the monster soon launched the cane into the sea, before grabbing Sly. With the monster beginning to crush Sly, an outgunned Bentley was forced to escape to the other Cooper Gang members.
As he continued to be crushed, Sly's life began to flash before his eyes. Eventually, the flashbacks started to recount how he and Bentley expanded the Cooper Gang for the now ill-fated Cooper Vault heist, starting with Murray being re-recruited.
- During the binocucom introduction, the identities of all of the Cooper Gang members, except for Sly and Bentley, are hidden in order to prevent spoilers. However, Murray's subtitles are still in his trademark pink color.