If you decide to recruit the mysterious Vincent, you must open the safe in the Shinra mansion within 20 seconds. Use the directional buttons to move the tumbler. The combination is right 36, left 10, right 59, and right 97. As with a real combination lock, do not fly past the target number. Once you open the safe, you'll need to defeat Lost Number. After you defeat him take the key and visit Vincent in the room with the coffins, located behind a secret door west of the mansion's library in the basement. Examine the center coffin, Vincent will gain consciousness. Explain your quest regarding the evil Sephiroth. After Vincent returns to the coffin, speak to him again and talk about himself. He will join you when you leave the room.