When the Great War of 2077 broke out, the Cabinet Nuclear Alarm system alerted cabinet members of the ensuing nuclear exchange and which government fallout shelter to take cover in. However the system had been tampered with and most of the members removed in questionable circumstances.
The Secretaries of the Interior and Treasury were some of the only cabinet members sent alerts, with orders to report to the Whitespring bunker alongside the Secretary of Agriculture Thomas Eckhart. The Secretary of the Interior died soon after arrival, and with contact lost with Raven Rock as well as the president at Control Station ENCLAVE, the Treasury Secretary prepared himself to be the acting president and leader of the Enclave within the bunker per the chain of succession.
However simply making it to a fallout shelter didn't guarantee survival, as the secretary soon found out. Thomas Eckhart had other plans, ones that involved him being in charge, and had his subordinates isolate then execute the Secretary. Eckhart then gathered the bunkers occupants and informed them of the loss of contact with the rest of the Enclave as well as the secretary's death of "radiation poisoning", claiming control for himself.
The final Secretary of the Treasury is only mentioned in Fallout 76.