Dean Baker is driving home in a major downpour; he is coming back from procuring his Christmas tree which is taking up the greater part of the front and backseat of his car. He is mentally reviewing the letter he composed to his sister's family in Xenia, Ohio, advising them that he won't be able to visit this Christmas.
He is forced out of his daydream when a body curled up in an army poncho in the middle of the road looms on the immediate horizon. It is open to conjecture whether this perilous stunt is an unorthodox hitchhiking ploy versus a bona fide suicide attempt. The deed's perpetrator is Walter, an apparently orphaned drifter of approximately college age.
Baker's car stalls out as a result of the panic braking episode, but after a couple of weak cranks, the engine turns over again, and Baker decides to give the poor fellow a ride and to put him up over the Christmas holiday [after learning he has no family to visit and no preferred destination].
On the way to Baker's house, Walter begins singing the hobo ballad "Big Rock Candy Mountain" which becomes a recurrent theme throughout the episode [including a baroque instrumental version that plays under the opening credits]. Upon arriving at the Baker household, the unlikely duo unloads the Christmas tree. The dean's longtime housekeeper, Mrs. Samantha Humphrey, immediately views the holiday house guest (who has no last name) with a suspicious eye. Baker instructs her to provide Walter with some clean and dry clothes.
Channing chairman of the Bio-Physics department, Prof. Lucas, is waiting in Baker's study when he arrives. Lucas is eager to force the resignation of the elder [and one-time Nobel prize-winning] Prof. Fyfe. Lucas believes Fyfe's costly and sprawling research project [involving electrical detection of emboli] has not made any significant progress in the last four years [and the esteemed researcher seems only to be replicating work already done [and published by] Prof. Skinner at Harvard.
No sooner has Walter arrived at the Baker House than he makes an impromptu field trip to a local cocktail lounge where an unsavory crowd is gambling on the outcome of table shuffleboard matches [which just happen to be Walter's specialty].
Walter is in the process of hustling a few dollars when Baker catches up to him. Baker (who rather surprisingly is known by the bookie who is collecting the bets) even wagers a few dollars on Walter [and wins!]. Baker and Walter return to the homestead; they put up the Christmas tree, and Walter takes a leisurely bath. The dean then gives Walter a tour of the Channing campus.
Along the way, Walter admires some sculpture and other objet d'art. Baker inquires as to Walter's interest in art. He mentions something about once ordering a correspondence course from a matchbook cover, but never having received it. He then produces from his pocket a drawing he did of Mrs. Humphrey, which is strikingly good. Baker offers to sponsor him as a special art student at Channing for the upcoming semester. The young man advises the dean that he will consider the offer.
Prof. Lucas actively confronts Fyfe informing him of the impending necessity to shut down his experiment [Lucas actually flips a switch causing part of the equipment to power down, thus jeopardizing five months of the older scientist's work (not to mention, inducing rigor mortise in one of the mice!), and he further threatens to completely dismantle the rest of the lab]. He also presents Prof. Fyfe with Prof. Skinner's published work that seemingly renders his experiment obsolete. Prof. Fyfe apparently has not been keeping up with the literature in his field. Dean Baker has been resistant to acting on Lucas' complaints about his old friend Fyfe. Lucas has phoned Baker several times while he has been busy with Walter. Baker had Humphrey take messages in an attempt to blow him off. Lucas finally gets through and plays his trump card-the literature demonstrating that Skinner's break-through of the previous year, had made Fyfe's experiment superfluous.
Prof. Lucas visits his late wife's grave site [her death, four years earlier, roughly corresponds to the date of the deterioration of the efficacy of his work]; Baker catches up to him there and discusses the content of his latest conversation with Department Chairman Lucas. Fyfe emphatically states that he will not resign voluntarily and that the firing of a Nobel prize winner would certainly be an embarrassment for Channing in the academic community. Leaving a farewell note for Dean Baker in his study, Walter hits the road again.
His first stop is at the "Naked Bulb" cocktail lounge [the site of his previous shuffleboard exploits]. The poor souls there [with no other place to go on Christmas] are sharing their sad stories. Walter tries to cheer up the denizens of the lounge, offering them small gifts of potato chips and inviting them to join him for a friendly shuffleboard match. He makes little progress as the establishment is closed for Christmas until 5:00. He hitches a ride back by the Baker house. Peering in the window, he is surprised that the dean's party is not underway. He checks with Samantha who advises him that the dean has been quite depressed since he read Walter's goodbye note. He also received several cancellations for the Christmas party, and then phoned all the other invited guests to say that he didn't feel up to hosting the party, and now he has gone out for a walk to clear his head.
Samantha calls Walter's attention to the art book Dean Baker bought him as a Christmas present. Walter departs again (with the book under his arm) after pumping Samantha for the names of the Christmas "party poopers". The first two mentioned are Lucas and Fyfe. Walter mulls around the rat cages in Fyfe's lab while Fyfe is reading Skinner's paper. Both professors have apparently had changes of heart. Lucas comes in, announcing that he is withdrawing his request that Fyfe resign [and after spending the holiday with his precious wife and children (as Walter had previously suggested to him when they met briefly in the Baker study), he can well appreciate the devastation wrought by the death of Fyfe's wife]. Fyfe says that he has decided to tender his resignation to Baker, as he now appreciates what an anachronism he has become. Walter then makes his presence known, laying a "guilt trip" on the two reconciled colleagues for "bugging out" on their old friend's Christmas party. They provide him names of other faculty members who were invited, and Walter sets out to find them. Cut to Baker's house; he is discussing Walter's brief reappearance with Samantha, when all of the reassembled partygoers [headed by Fyfe and Lucas, and including series co-star Prof. Howe who is relegated to a one-minute cameo in this episode] come knocking at door. Baker warmly welcomes them.
Samantha goes out on the porch, looking for Walter as she knows he orchestrated it all. She doesn't see him, but he is there hiding behind a tree as the revelers inside break out into Christmas carols. Fyfe presents Baker with his resignation letter. Baker tears it up and forcefully encourages Fyfe to start a new research project. Across the room, Lucas observes this and smiles approvingly.
At the "Naked Bulb", Walter is engaged in a rollicking shuffleboard match with the now-cheerful but still-motley crew of lounge regulars. Back at the Baker home, as the partygoers are saying their goodbyes, Prof. Howe relays that Walter had asked him to wish Dean Baker a Merry Christmas with the additional cryptic message that "Everyone should go home for Christmas."
Dean Baker, at the wheel of his car, mentally reviews the new letter to his sister, advising that he will be coming to visit her for the holidays, after all. At the side of the road is a young drifter who is warming his hands by a fire and singing "Big Rock Candy Mountain". He has posted a cardboard sign saying: "Who In The World Would Be Going To Xenia, Ohio?" As the car slows, we are left assuming the two friends will now be reunited for at least the amount of time it takes to reach that destination.