At the start of the film, Cathy leaves her parents' overcrowded rural home and hitchhikes to the city, where she finds work and meets Reg, a well-paid lorry driver.

The loss of income and birth of baby Sean force them to leave their flat, and they are unable to find another affordable place to live that permits children.

However, she dies suddenly and an agent of her nephew and heir appears at the door demanding all the back rent, which they are unable to pay.

The play was written by Jeremy Sandford, produced by Tony Garnett and directed by Ken Loach, who went on to become a major figure in British film.

Loach employed a realistic documentary style, using predominantly 16 mm film on location, which contrasted with the vast amount of BBC drama of the time, the bulk of which was entirely shot in a television studio.

The cinematographer was Tony Imi, whose innovative use of a hand-held camera to take moving action shots and close-ups gave Cathy Come Home almost a feel of a current affairs broadcast and a realism which was rare in British television drama at the time.

Imi commented: "I was stuck in a rut after working on Dr Finlay's Casebook and Maigret – standard BBC productions.

It was broadcast in the United States on National Educational Television (NET) on 28 March 1969, capitalizing on Carol White's international success in Poor Cow and I'll Never Forget What's'isname in 1967, and The Fixer in 1968.

The play broached issues that were not then widely discussed in the popular media, such as homelessness, unemployment, and the rights of mothers to keep their own children.

Its hard-hitting subject matter and highly realistic documentary style, new to British television, created a huge impact on its audience.

[3] In a 2000 poll of industry professionals conducted by the British Film Institute to determine the BFI TV 100 of the 20th century, Cathy Come Home was voted second (the highest-placed drama on the list), behind the comedy Fawlty Towers.

Though it was not connected to the programme, "the film alerted the public, the media, and the government to the scale of the housing crisis, and Shelter gained many new supporters.