The Day of the Triffids is a BBC miniseries adaptation of John Wyndham's novel of the same name. The novel had previously been adapted by the BBC in a 1981 miniseries.

Driving home one night in London, a woman hits a man who shouldn't be there.

In the Yorkshire countryside, working-class tomboy Mona meets the exotic, pampered Tamsin. To seal their friendship, Mona introduces Tamsin to her born-again Christian brother and helps her spy on her adulterous father. Bound together by their secrets, the two girls see their friendship deepen and enter into dangerous waters.