Nearly 50 years after Mary Jo Kopechne‘s body was found in a submerged car belonging to Sen. Ted Kennedy, ABC is devoting an hour to her strange death.

In an exclusive preview (above) from “The Girl In the Car,” the third episode in the network’s six-part docuseries 1969, family and friends of Mary Jo recount the day of her Pennsylvania funeral. Outside massive crowds had gathered hoping to spot Kennedy, who was sporting a conspicuous neck brace, and wife Joan Kennedy.

“Mary Jo’s parents were in a world of their own because they were heartbroken and their daughter was gone, their only child was gone,” her cousin recalls in the preview.

On the night of July 18, 1969, Kennedy, then 37, drove his car off a narrow wooden bridge on Chappaquiddick Island, just off of Martha’s Vineyard in Massachusetts.

He escaped. But Kopechne, a 28-year-old former aide to Robert F. Kennedy, was trapped inside and died.

Ted waited nine hours to report the incident — and only did so after his car had been spotted by two fishermen and then located underwater by a diver and the local police.

RELATED: All About Chappaquiddick, the Shocking Kennedy Scandal That Left One Woman Dead

There had been a reunion party the night of the wreck attended by six men, including Ted, and six women who had worked for Robert, known as the “Boiler Room Girls” because of the windowless office in which they worked.

Ted claimed he left the party around 11:15 p.m. in order to drive Kopechne back to the ferry to return to Martha’s Vineyard. But he made a turn that led him in the opposite direction of the ferry landing, leading many to doubt his version of the events.

He later said that he “made immediate and repeated efforts” to rescue Kopechne but was unsuccessful, “succeed[ing] only in increasing my state of utter exhaustion and alarm.”

In the ABC special airing Tuesday, John Farrar, the diver who pulled Kopechne’s body out of the water, as well as one of the local investigators, share why they believed Kopechne could have been saved had the crash been reported sooner.

“Her story has largely been lost to history, as the media and the public focused on the man whose career was forever damaged by the accident, rather than the bright young woman who did not live to tell us what really happened on that mysterious night,” ABC said in a news release about the episode.

RELATED: 10 Shocking Things You’ll Learn About the Chappaquiddick Scandal in Cover-Up

The wreck in Chappaquiddick and the questions surrounding it are also the subject of Cover-Up, PEOPLE’s first podcast series with Cadence 13, released last year. The series is available on Apple Podcasts, Google Play, Spotify and other platforms.

1969‘s “The Girl in the Car” airs Tuesday (10 p.m. ET) on ABC.