Agent Chaimson was a S.H.I.E.L.D. operative assigned to the Hub. During the HYDRA Uprising, Chaimson worked with Victoria Hand to maintain the security of the Hub against HYDRA. While transporting the HYDRA infiltrator, John Garrett also known as the Clairvoyant, Chaimson was murdered by Grant Ward.
Chaimson was one of five other agents that Victoria Hand knew was not a HYDRA sleeper agent and had pledge his loyalty to S.H.I.E.L.D. He was at the Hub when she gave the order to kill Phil Coulson's team and John Garrett when they would arrive there aboard a reprogrammed Bus. When Hand tested the loyalty of Jemma Simmons and Antoine Triplett, she threatened them with death if they were not HYDRA agents. Triplett took Chaimson and held him at gunpoint, threatening to kill him in response, believing he was a HYDRA agent. That response caused Triplett and Simmons to pass her test, proving their loyalty to S.H.I.E.L.D..