Timothy Sloan is a mild-mannered estate investigator, and the foster brother of Jason Greenfield. He became a person of interest after Peter Collier and his organization, Vigilance, were after him for information on Jason's whereabouts.
Jason had apparently died of a heroin overdose (Sloan was investigating Jason's home while Finch went undercover as his assistant), but in reality, Jason got himself into trouble with Vigilance. He was a hacker member at the group but decided to get away after Collier's decision to kill Wayne Kruger instead of just giving him a message. Afterwards, Jason became a prisoner when trying to reveal information and was taken to a CIA black site.
Sloan was captured by Collier and his men and was interrogated aboard a truck. Reese arrived and found Sloan, Collier, and Sameen Shaw, who was captured by Root. During a shootout, Sloan and Greenfield look at each other for a few seconds until Root takes Jason with her to escape. Collier held Sloan at gunpoint, and told Reese he could either pursue him or save Sloan. Collier shot and critically injured Sloan, and escaped while Reese tended to Sloan's injuries.
The next day, Sloan, in crutches, thanked Reese and Finch for saving his life. Jason, who was saved by Root under instructions from The Machine, called Sloan from South America and happily told him he was doing well, and hoped to see him. (“Mors Praematura”)