She was born Adelaide Proctor in Surrey, England, and studied at Somerville College, Oxford University.
H. P. Plumptre became an important figure in the local Anglican church, rising to become rector of St. James Cathedral.
She became Director of Supplies of the Canadian Red Cross in September 1914 and remained in that role for the whole of the First World War.
She took the lead in organizing the logistics of the Red Cross' wartime relief efforts across Canada and overseas.
In 1941, she attempted to become the first woman to win a seat on the powerful Board of Control, but lost by a few hundred votes.