Plot

A lazy, irresponsible young clerk (Sir Tom Courtenay) in provincial Northern England lives in his own fantasy world and makes emotionally immature decisions as he alienates friends and family.

Going nowhere fast, Billy Fisher, an incorrigible fantasizer, dreams incessantly of escaping his drab existence and humdrum routine work as an undertakers' clerk in Yorkshire. Seeking refuge from his working-class family and not one but two demanding fiancees in the imaginary country called Ambrosia, more and more, Billy finds himself cut off from reality, picturing himself as its ruler and hero. Then, as Billy's fabrications grow increasingly wilder and problems start piling up, lovely, happy-go-lucky Liz enters the young day-dreamer's life, offering a way out of this fine mess. However, new beginnings are always scary, and Billy must make up his mind: it's either a fresh start in London or an endless beautiful lie in Ambrosia.—Nick Riganas

Living with his middle class judgmental parents and his ailing maternal grandmother in Yorkshire, and working as a clerk at Shadrack and Duxbury Funeral Furbishers under Mr. Shadrack himself, young adult Billy Fisher often daydreams as a means of escape from what he considers his less than satisfying life, and in the process will tell bald-faced lies to advance his fantasy narrative. While those daydreams are often what he is feeling at any given moment in what he would like to happen in needing to get out of a predicament of his own making, he has a recurring fantasy of being the military ruler of a fictional country called Ambrosia, those scenarios mostly in grand pomp and circumstance for him. The latest lie he is perpetuating is that he has been hired by comedian Danny Boon to be his script writer, entailing a move to London. While he did indeed write to the celebrity in his quest to be a writer of some sort, he only got a noncommittal form letter from Boon's representatives in return (i.e. no one in Boon's entourage actually read what he sent Boon, including Boon himself), he planning on approaching Boon, who coincidentally is in town, to nail down the details of employment. Another one of the predicaments he's gotten himself into is that he is stringing along two different women, Barbara and Rita, who don't know or know of the other, and who, also unknown them, are "sharing" one engagement ring, which Billy has to manage to transfer between them in some manner through more lies. The other thing that neither Barbara or Rita knows is that Billy loves neither of them, getting married which he is feeling pressured to do by his parents. While his actions alienate more and more people, the person who does understand what he is feeling is recently returned free-spirit Liz, an ex-girlfriend who, in feeling much what he has felt about the dead end life in Yorkshire, has left in running from Yorkshire as opposed to running to somewhere or something else, for her the process more important than the outcome.—Huggo

Billy (Tom Courtenay), a young British clerk in a gloomy North Country undertaker's office, is bombarded daily by the propaganda of the media that all things are for the asking. This transparently-false doctrine, coupled with the humdrum job and his wild imagination, leads him on frequent flights to "Ambrosia", a mythical kingdom where he is crowned King, General, lover, or any idealized hero the real situation of the moment makes him desire. His vacillating commitment and post-adolescent immaturity have created situations which make Ambrosia all the more attractive. He's succeeded in becoming engaged to two different girls simultaneously, while in love with a third, Liz (Julie Christie). He's in hot water with his employer, having spent a rather large sum of postage money on his personal frivolities. Last but not least, his dream of becoming a highly-paid, famous scriptwriter in London seems doomed. The only person in his life capable of bringing him down to Earth is Liz, and she's having a difficult time. Finally, he gets his life sufficiently in order to leave for London with his true love, but still hasn't gotten to grips with the real world. He leaves the train to buy milk from a vending machine and watches the train slowly pull out for London with Liz aboard. He returns to the more comfortable shelter of his parents' home, Ambrosia, and his imagination.—alfiehitchie

Billy Fisher (Tom Courtenay) works by day as a clerk in an undertaker's office but lives his dreams in his own imaginary world. He is having such a dream when the film begins in which he is a returning war hero passing through crowds of applauding people. He is soon brought back to reality by his mother's call for breakfast. He sits at the table to eat with his father and grandmother who tell him that he should grow up and live in the real world.

Billy arrives late to work and is questioned by his employer, Mr Shadrack (Leonard Rossiter) about the disappearance of a large number of calendars that he was meant to deliver to clients. The calendars are in fact locked away in a wardrobe in Billy's bedroom.

Billy is also engaged to not one but two local young women, the sweet and virginal Barbara (Helen Fraser) and the rough and ready Rita (Gwendolyn Watts). Unbeknown to both women, they share an engagement ring. It is the freewheeling Liz (Julie Christie) who has just recently returned from London however that Billy is truly in love with.

Billy comes to hear that comedian Danny Boon is making an appearance in town and tries to show him a script that he has written but is quickly dismissed by Boon. Despite this, he still tells people that he is going down to London to write scripts for the comedian.

Under pressure, Billy arranges a date on the same night with both Rita and Barbara in the same venue, the local dance hall. It is not long before Billy's double engagement is discovered when Rita sees the ring on Barbara's finger. He quickly makes an exit as a catfight ensues. Whilst on the upper level of the ballroom, he encounters Liz and soon leaves with her. As they are walking outside, Liz asks Billy to accompany her to London that evening. He accepts and heads promptly home to pack his bags. Billy's father (who has been trying to reach him by phone at the ballroom) tells him that his grandmother has been taken to hospital. Billy heads to the hospital en route to the train station where he finds his mother in the waiting area. It is not long after his arrival that they are told that his grandmother has just passed away. Billy tells his mother of his plans to go to London and continues on to the station.

He arrives at the station and meets Liz. They board the train and Billy decides to rush back to the station to get them both a carton of milk for the journey. Although hesitant, he moves quickly but just misses the train. A disappointed Liz looks on from the window. The film's final shot sees Billy walking back up a dark and deserted road to the family home.