On this day in 1980, J.R. Ewing, the character millions love to hate on television’s popular prime-time drama Dallas, is shot by an unknown assailant. The shooting made the season-ending episode one of TV’s most famous cliffhangers, inspired widespread media coverage and left America wondering “Who shot J.R.?” for the next eight months. On November 21, 1980, the premiere episode of Dallas’s third season solved the mystery, identifying Kristin Shepard, J.R.’s mistress (and his wife’s sister), as the culprit.

The CBS television network debuted the first five-episode pilot season of Dallas in 1978; it went on to run for another 12 full-length seasons. The first show of its kind, Dallas was dubbed a “prime-time soap opera” for its serial plots and dramatic tales of moral excess. The show revolved around the relations of two Texas oil families: the wealthy, successful Ewings and the perpetually down-on-their-luck Barnes clan. The families’ patriarchs, Jock Ewing and Digger Barnes, were former partners locked in a years-long feud over oil fields Barnes claimed had been stolen by Ewing. To make matters more interesting, Ewing’s youngest son Bobby (Patrick Duffy) and Barnes’ daughter Pam (Victoria Principal) had married, linking the battling clans even more closely. The character of J.R. Ewing, Bobby’s oldest brother and a greedy, conniving, womanizing scoundrel, was played by Larry Hagman.

In the wake of the season-ending cliffhanger episode, “A House Divided,” audiences were hard-pressed to guess who was responsible for the shooting; J.R. had a host of enemies. That summer, the question “Who Shot J.R.?” entered the national lexicon, becoming a popular T-shirt slogan, and heightening anticipation of the soap’s third season, which was to come in the fall. Much to the dismay of Dallas fans, the premiere was delayed because of a Screen Actors Guild strike. When it finally aired, the episode revealing the shooter became one of television’s most-watched shows, with an audience of 83 million people, and helped put Dallas into greater worldwide circulation. It also popularized the use of the cliffhanger by TV writers.

The shooting of J.R. was not Dallas’s only notorious plot twist. In September 1986, fans learned that the entire previous season, in which main character Bobby Ewing had died, was merely a dream of Pam’s. The show’s writers had killed the Bobby character off because Duffy had decided to leave the show. When he agreed to return, they featured him stepping out of the shower on the season-ending cliffhanger, and then were forced the next season to explain his sudden reappearance. The last new episode of Dallas aired on May 3, 1991. A spin-off, Knots Landing, aired from December 27, 1979, until May 13, 1993. Dallas remains in syndication around the world.