From Wikipedia:
That Certain Summer is a 1972 American television movie directed by Lamont Johnson. The teleplay by Richard Levinson and William Link was the first to deal sympathetically with homosexuality. Produced by Universal Television, it was broadcast as an ABC Movie of the Week on November 1, 1972. A novelization of the film written by Burton Wohl was published by Bantam Books.
Divorced San Francisco contractor Doug Salter is looking forward to a summer visit from his fourteen-year-old son Nick, who lives in Los Angeles with his mother Janet. What the boy doesn't know is that his father is gay and committed to Gary McClain, his life partner of several years, who opts to move out temporarily in order to keep Nick's possible suspicions at bay. When he finds evidence of his father's secret life, the teen — filled with shame and disgust — runs away. Once reunited with his son, Doug attempts to explain his sexual orientation to him, with decidedly mixed results.
Principal cast
* Hal Holbrook ..... Doug Salter
* Martin Sheen ..... Gary McClain
* Scott Jacoby ..... Nick Salter
* Hope Lange ..... Janet Salter
* Joe Don Baker ..... Phil Bonner
Principal production credits
* Producers ..... Richard Levinson, William Link
* Original Music ..... Gil Melle
* Cinematography ..... Vilis Lapenieks
* Art Direction ..... William D. DeCinces