Carol Lynley, a former child model who had an intense film acting career mirroring the country’s transformation from the modest Eisenhower era into the sexually frank 1960s, died on Tuesday at her home in Los Angeles. She was 77.

The cause was a heart attack, said Trent Dolan, a friend.

Ms. Lynley may be best remembered as the naïve, soft-spoken adolescent who becomes pregnant by her equally wide-eyed boyfriend, played by Brandon De Wilde, in the 1959 film “Blue Denim.” It was a role she had originated on Broadway the year before, when she was 16.

Ms. Lynley made at least a half-dozen Hollywood movies over the next eight years, but by the time she was in her mid-20s her star had faded, and she was never directly in the public eye again.

Still, she did make a notable if brief comeback in 1972, when she turned up wearing hot pants and go-go boots in the disaster movie “The Poseidon Adventure,” singing (or at least lip-syncing) the Oscar-winning song “The Morning After.”