[5] Plunkett is the holder of a peerage title, and holds Dunsany Castle, one of the longest-inhabited houses in Ireland, and its remaining estate.

Plunkett became an advocate for rewilding in 2014 and has dedicated around half of the ancestral estate in County Meath as Ireland's largest private nature reserve.

Plunkett was born on 8 March 1983 in New York City, where his parents were living at the time operating an architectural and design studio.

[8] Encouraged by his parents, he later returned to the idea of working in film, and pursued an intensive course in Digital Video[5] with an emphasis on practical skills, at the SAE Institute, from the Amsterdam campus of which he graduated with a diploma.

[6] He continues to live at Dunsany Castle, on its estate of over 1,500 acres (610 ha), near Dunshaughlin and Kilmessan, about 30 km (19 mi) north of Dublin.

[10] While the estate was reduced in size under the Irish Land Acts, with much farmland transferred to tenants, it remains a substantial landholding, between Dunshaughlin and the Hill of Tara.

He then returned to Ireland, producing Guerrilla, directed by Blaine Rennicks and starring Jack Lowe and Darren Killeen, on the Dunsany lands from winter 2009.

[12][13] The low-budget film, with a crew of 40, was based on a concept of Ireland under martial law after social collapse in Europe in 2013, and was released in 2010.

[8] Plunkett has used his estate lands and buildings, some partly ruinous, as locations for much of his filming after Guerrilla, including for Prey and Walt.

[10] Plunkett received external private funding for his next film, a post-apocalyptic horror movie titled Out There, co-writing the script with his brother Oliver.

Small groups are allowed a visit by arrangement but Plunkett has said he does not plan structured paths and signage, or visitor attraction facilities such as a café.

[28] Having previously been in a relationship with Irish actress Emma Eliza Regan,[9] Plunkett met his partner, occupational therapist Laura Dillon, in Mullingar.