"A House Divided" is the actual name of the most famous episode in television series history, but it became known in the television gossip circles as "Who Shot J.R.?". The original air date of the program is March 21, 1980.

The show begins by J.R. being visited by a man named Alan Beam, and a policeman Harry McSween. A confrontation between J.R. and Alan results in the threat of “rape” being charged against Alan. He is then promptly removed from the building.

Other people are voicing their displeasure that J.R. is running rampant, without any regard for anyone but himself. Little brother Bobby threatens to leave Southfork Ranch. Alan is seeing Kristin at her apartment when bad cop McSween arrives with a warrant for her arrest because of prostitution. Kristen makes a verbal outburst that she promises to kill J.R. and Alan tells her to take a number.

At various locations, people are designing their own ideas to stop J.R. from continuing his ways. Sue Ellen takes a gun with her on her way to see Dr. Elby, and Vaughn has a scream fight with Ewing on the telephone. Cliff Barnes goes to the grave of his father, and makes the comment that he must stop J.R. for good. The tension mounts and the list of suspects grows ever longer for the climax that is soon to happen.

In his office, alone at night, J.R. answers his telephone, but the caller hangs up. In the darkness of Ewing Oil, an unseen figure is seen moving and J.R. decides to leave the safety of his office to investigate. As he opens the door to his office, three shots ring out from an assassin's gun, and J.R. hits the floor. Who? Who? Who shot J.R.?