Theo Grey is a criminal and information enthusiast who has an unfortunate habit of lying to too many people. His overarching goal since he came to Los Santos has been to set up a robbery on the Vangelico's Jewelry store in Vinewood, including finding a crew and illegal guns to do it with.
On December 30th 2017, Theo met with Mav Doretto and James O'Reilley on a pier off of Grapeseed Avenue on his request. He had called the meeting to see if he could get illegal guns from them, which he knew they had after an incident where he ripped James out of a tow truck, robbed him at gunpoint, and found his illegal pistol. The meeting ended in Theo being forced to sit at the end of the pier and Mav using an automatic gun to blow out Theo's kneecaps. Theo survived after a local called in the shots and an ambulance arrived.
On January 20th 2017, Maxine Devereux met with Theo at the Vinewood Bowl theater to discuss who shot Lil Tuggz. Theo had been collecting information for Maxine on Lil Tuggz and other people, however, many people were now after him because of his habitual lying. During the conversation, Maxine gave him an ultimatum: Go into hiding for a while to lose the heat or die now. Theo agreed with this and admitted that he doesn't want to die. Maxine ended up stabbing him, grabbing his phone, and leaving him to die for lying to her and others. Unknown to Maxine, Skyler Rose tried to call out to her as she was leaving, but was not heard. She tortured Theo by sticking her finger into his stab wound and kicking him repeatedly as he lay bleeding out, asking why Maxine stabbed him. Theo reveals that she wanted information about guns, Isabelle Knight's death, and his lies. Theo recovered with some lasting scarring, though he had little recollection of the event and no recollection of Skyler being there beside her haunting voice in his head and in his nightmares.
On January 30th 2017, Theo called a taxi down to the docks to go up to Rockford Hills. Skyler Rose arrived with Preston Landor driving the taxi. They stop at a crate ship and Preston tells Theo to get out of the car with a gun to his head. He orders him onto the ship while telling Skyler, "I told you this man stabbed me the other day", referring to an incident where Theo stabbed Preston in Legion Square for giving him bad information about Lil Tuggz's shooting. Skyler tells him that she is going to call the cops. Preston claims it is a citizen's arrest for crimes that Theo had committed and not been arrested for, specifically the stabbing of Dan Dorfman and the mental torture/stalking of Jazmine T. Cops eventually arrived as Theo challenged Preston to shoot him and both parties were arrested.
On February 3rd 2018, Theo was offered to join The Tribe by Baada Ka as an information broker. He accepted under the condition that he mend old and broken relationships so that he would not be under the threat of being killed anymore.
On February 26th 2018, Theo called Maxine to come to the beach across from the motel in Paleto to talk to her personally. They discussed past events, especially the reasoning behind the Vinewood Bowl incident. He expressed that he always thought of them as friends and Maxine agreed. During the conversation, Maxine ended up turning away from him for a moment. Theo said "I'm sorry", and as Maxine was turning back around, shot her twice in the shoulder. He also stabbed her in the stomach, claiming that it was for the unfinished business in the Vinewood Bowl. She survived.
On March 6th 2018, Theo received a text from Joey Uldrich to meet him at the dam for a talk. They talked about Theo's past and present plans, but not much information was shared. During their conversation, Maxine Devereux, Bruce Greenwell, and Mav Doretto came out from inside the dam. With no words, Maxine slashed Theo across the face and stabbed him in the stomach. She took his phone and wallet, then shot him in the shoulder. Mav commented, "Long Live the Chief" in reference to Baada Ka kicking him out of the Tribe for stabbing Maxine a second time, then they all left. Theo survived.
On March 9th 2018, Theo kidnapped Zoey Lyrais and held her hostage as he robbed the Vangelico's Jewelry store in Vinewood. While he was robbing the store, he mentioned to Zoey that he had a promise to keep to his brother, who was "the only family he had left". He demanded $20k and a getaway car, which was provided by Trooper Bucky Savage. Theo hit Zoey in the head with his gun and fled in the car. On the way out of the alley, he hit spike strips and crashed, causing him to flee and get gunned down by troopers in a firefight. He was declared DOA (dead on arrival) at Mount Zona Medical.