Peter fell in love with reading at a young age and started writing short stories as a boy. He wrote plays in high school and at Johns Hopkins University, where he studied in a department devoted to writing, speech and drama, graduating with a bachelor’s degree in 1956.
He married Lucille Warnock in 1957.
Mr. Fischer did not become a full-time writer right away; instead he made a living in direct mail, as an insurance investigator and as a trade magazine editor. He also published a monthly magazine, Sports Car News, out of his house in Smithtown, N.Y., on Long Island.
At 35, he got his screenwriting break. He had written a script about a dystopian future in which couples are permitted only one child and people over 65 are denied medical care. With help from his brother, Geoffrey, a casting director at Universal Television, the script found its way to the producer Aaron Spelling and was made into an ABC movie, “The Last Child” (1971), with Michael Cole and Janet Margolin as a couple who are willing to defy the law to have a second child after the death of their firstborn.
He then wrote episodes of several Universal series, including “Marcus Welby, M.D.,” “Owen Marshall, Counselor at Law,” “Kojak,” “Baretta” and “Columbo,” for which he also worked as a story editor.
Three shows Mr. Fischer created or co-created had short runs: “The Eddie Capra Mysteries” (1978), starring Vincent Baggetta as a lawyer; “The Law & Harry McGraw” (1987), a spinoff of “Murder, She Wrote” starring Jerry Orbach as a private investigator; and “Blacke’s Magic” (1986), starring Hal Linden — the collaboration with Mr. Link and Mr. Levinson that CBS did not want. (It ended up on NBC.)
In addition to his grandson, Mr. Fischer is survived by his daughter, Megan McElrath; four other grandchildren; two great-grandchildren; his half sisters, Paula Shorts and Stephanie Donnelly; and his half brother, Stephen Fischer. His wife died in 2017. His sons also died before him — Stephen in 2014, Christopher in 2020.