At one stage, he lived in Harrow, Middlesex.
The 1901 Irish Census records Plunket living in house 9, Straheglin, Belturbet, Co. Cavan with his grandfather, James H Mahaffy JP.
By 1911, the family are recorded as living in house 29.1 Antrim Road, Clifton Ward, Belfast. Plunkett describes his occupation as a Bank Clerk.
The Belfast News Letter of 30th May 1917 reports: