Cheers is a small bar in Boston, MA. As owner Sam Malone opens up, a couple enter the bar. Professor Sumner Sloane and his fiance Diane Chambers are to go to Barbados to be married, but Sumner's ex-wife still has the wedding ring. Sumner asks Sam to keep an eye on Diane for him whilst he goes and fetches it.
Sam tries chatting up Diane but she's not interested. The other employees at Cheers arrive for work - waitress and single mom Carla Tortelli, and bartender Ernie "Coach" Pantusso, who was Sam's baseball coach back in the days when Sam was a relief pitcher for the Red Sox. As the bar gets busier and more people wonder who she is, Diane hopes Sumner will return eventually.
Sumner comes back a few hours later and says he hasn't got the ring, but then his ex-wife calls and says she's got it, so he once again leaves Diane in Cheers whilst he goes to fetch it. He asks Diane to call the airport and put their flight back a bit. Once again he is gone a long time, and Diane starts to worry that he may have left her. She tells her problems to Sam, who thinks Sumner is "goofy". Diane defends her fance, but Sam tells her he's probably on a plane with his ex-wife. Diane calls the airport and finds out that "Mr and Mrs Sloane" have already left.
Heartbroken, Diane prepares to go home, but realises she now hasn't got a job (she was Sumner's teaching assistant). Feeling sorry for her, Sam offers her a job at Cheers as a waitress. Diane reluctantly takes the job, as she isn't qualified for anything else, and is welcomed into the Cheers family.