Tony, a disaffected London office clerk (Hancock) catches the train to Waterloo Station each morning as he has done for 14 years. In the city he sits as one of many identical clerks in a dull office. Each worker wears a bowler hat and carries an umbrella. One day his boss (John Le Mesurier) catches him drawing faces instead of working, and he is asked to step into his office. His ledgers are full of poor quality caricatures of fellow workers. He is told to take the afternoon off but does not. He leaves at exactly 5.30pm as does everyone else.

Back at his lodgings, in a mid-terraced brick Victorian house, somewhere in outer London, Tony dons his artist's smock, and resumes work on his masterpiece, "Aphrodite at the Waterhole"... a truly horrendous but huge sculpture. His landlady Mrs Cravat (Irene Handl) complains about the hammering noise. He explains he cannot afford a model and it represents "women as he sees them". She threatens to evict him if he does not remove the statue. As he remonstrates with his copy of Van Gogh's self-portrait on his wall, the floor creaks and the statue falls through, luckily missing his landlady below.

In his office attire he goes to a local cafe seeking a coffee "with no froth". This annoys the owner, who tells Tony he has just bought an expensive froth-making machine. Inspired by a poster on the wall Tony decides to go to Paris. He takes a train to Dover with his Aphrodite on a flat-bed wagon to the rear. She loses her head as the train goes through a tunnel. When, on arrival at the port, Tony sees the headless statue he is furious, but worse is to follow. While being loaded onto a ship it proves too heavy for its net, bursts through the bottom and is lost in the sea. Forced to accept the inevitable, he resolves to start again in Paris. On the ferry he throws his bowler hat and umbrella into the sea. Unfortunately it is raining heavily when he arrives in France.

Arriving in Paris, Tony walks along the River Seine and looks at the artists. In the evening he goes to a cafe in Montmartre and meets a group of English-speaking artists. Here he meets Paul, who speaks passionately about art. He orders a half litre of vin ordinaire and they drink together. Paul invites Tony to share his studio and flat, just up the road. The landlady Madame Laurent hears them enter and demands the rent. Tony loves the atmosphere in the studio. Tony is asked to critique Paul's paintings ... "Your colours are the wrong shape" he says.

Paul admires the childlike style of Tony's work: "infantile art". Josey, a red-haired, blue-lipped beatnik visits and invites Tony and Paul to a very large mansion, filled with artwork. Here the Dalí-esque owner, Jim Smith, is sleeping on the bookcase (because he is writing a book). At a party a group of young people all dressed alike hang on Tony's every word. They all think he is fantastic.

Inspired by Jim Smith, Tony starts sleeping on top of the wardrobe and brings a cow to live in the flat. He then tries his first Action painting. Paul decides to leave, and gifts Tony his art.

As his reputation spreads he is visited by Sir Charles Broward, an art collector and buyer who is attracted to Paul's work. Sir Charles asks Tony if Paul's works are his and Tony says they were "a gift". This is misinterpreted. Tony's own work is labelled awful. After the first exhibition he goes to a posh restaurant with Sir Charles. He orders egg and chips... when pushed to choose something more he orders snails, egg and chips and a cup of tea. Sir Charles takes Tony to Monte Carlo, where he goes to dinner with a number of rich guests. One wife, Mrs Carreras, wishes to be painted by Tony. Her husband, after some debate, commissions a sculpture.

Tony injures his fingers while hammering and later at dinner the wife hand feeds him, much to the embarrassment of all. Carreras offers to buy Tony's entire art collection for £50,000.

On the Carreras yacht, Tony dresses as a bird for the fancy dress party. Mrs Carreras dresses as a cat. She tells him she loves him. He rejects her and she threatens to shoot him. On deck, he unveils the statue to the horror of all - it turns out to be a copy of his Aphrodite - and Mrs Carreras accuses him of assaulting her. The statue drops through the ship and Tony escapes on the yacht's launch.

Still dressed as a bird, Tony goes to the airport and says he wants to fly to Britain. "Wouldn't you rather take a plane?" the attendant quips.

He returns to Mrs Cravat's, now finding Paul living with her and working in an office, though still painting as a hobby. Tony persuades Paul to lend him some new paintings, promising to explain later. Showing these paintings at the London exhibition, Tony reveals that Paul is the true artist and "the rubbish" is Tony's work. Leaving Paul to enjoy his newfound fame and fortune Tony returns to Mrs Cravat's and resumes work on his Aphrodite - with Mrs Cravat as the model.