The Doomsday Heist update focuses on a storyline where the GTA Online Protagonists are reunited by Lester Crest and a new character, billionaire Avon Hertz. The protagonist, Lester, and Avon unite with government agents, including Agent 14 and an unknown intelligence agent. Avon believes that an unknown foreign entity is trying to start a war and would put San Andreas and the United States under a "doomsday scenario". The crew are involved in several missions with the corresponding military-grade vehicles and weapons.
The The Doomsday Heist itself is a three act sequence of missions involving preparation and setup missions before undertaking heist finales in each act.