Teddy was an acquaintance of Leonard Shelby who attempted to assist him in his hunt for his wife's killer.
Teddy claimed he was a police officer, who was assigned to the rape of Catherine Shelby. He claimed Leonard was brain damaged by the attack and his wife couldn't live with it, so got Leonard to give her an overdose of insulin in order to test his amnesia. He killed her and was put in a home and transferred the incident to an old case of his, Sammy Jankis and his wife. Leonard got out of the home, believing his wife to have been murdered by the same man who gave him brain damage, and Teddy took pity on him and helped him find the culprit. He was a drug addict who had robbed the Shelbys for money, and Leonard killed him. Teddy took a picture just after the incident.
However, Leonard didn't remember that he had found the killer, and began hunting for John G. again. Teddy followed him, watching Leonard take pages out of the police report Teddy had given him in order to give himself a puzzle he could never solve. Leonard was staying at the Discount Inn when Teddy called him, explaining that he thought he had found the latest John G., a drug dealer. Teddy had set up a sale of amphetamines with a dealer named Jimmy Grantz, and was going to use Leonard to kill the dealer so he could take the money.
Leonard got scared over the phone, but Teddy used the picture of him after he had killed John G. to get back in touch with him. Teddy directed Lenny to an abandoned building where he killed Jimmy, then Teddy came to collect the money. However Leonard confronted Teddy and found out the truth, and decided to take Jimmy's clothes and car, along with all the money.
Teddy followed Leonard to Emma's Tattoos, where he tried to persuade him to change clothes and car and get out of town. Leonard didn't listen, and climbed out of the window of the parlour to avoid Teddy. Teddy then found him again at Natalie's house, Jimmy's girlfriend, and tried to persuade Leonard that she was using him as she was involved in drugs. He gave Leonard the address of the Discount Inn where he was staying.
Leonard then called Teddy and had him come to the Monterest Inn. Teddy arrived to find Dodd, one of Jimmy's associates, tied up in the cupboard. They agreed to march Dodd out of town and threaten him to never come back. Teddy again tried to get Leonard to change cars, but Leonard refused, saying he needed to find out what was going on.
The next morning Teddy caught Leonard outside Natalie's house, and they went for lunch. Teddy told Leonard that someone might be setting him up, but Leonard wouldn't listen. Later, Leonard called him from the Discount and asked to meet. They drove to the abandoned building again, and Teddy asked why they were going, but Leonard couldn't remember. Once they arrived, Leonard pulled a gun on Teddy and told him to beg his wife's forgiveness. Teddy pleaded with Leonard, asking them to go downstairs to see the body of Jimmy who he had already killed, but Leonard ignored him and shot him in the head, killing him.