On November 21, 1980, 350 million people around the world tuned
in to CBS television’s popular primetime drama “Dallas” to find out 
who shot J.R. Ewing, the character fans loved to hate. J.R. had been
shot on the season-ending episode the previous March 21, which
now stands as one of television’s most famous cliffhangers. The
plot twist inspired widespread media coverage and left America wondering “Who shot J.R.?” for the next eight months. The
November 21 episode solved the mystery, identifying Kristin
Shepard, J.R.’s wife’s sister and his former mistress, as the
culprit.

Kristin Shepard, J.R.’s sexy scheming sister-in-law/​mistress
was the guilty party. Shepard was played Mary Crosby seen
above.